Seadrill (SDRLF) 20-F 13 Apr 18 2017 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2017shares
Document and Entity Information [Abstract]
Entity Registrant Name	SEADRILL LTD
Entity Central Index Key	1,351,413
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)	504,518,940
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2017

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating revenues
Contract revenues		$ 1,888,000,000	$ 2,850,000,000	$ 3,957,000,000
Reimbursable revenues		38,000,000	66,000,000	113,000,000
Other revenues	[1]	162,000,000	253,000,000	265,000,000
Total operating revenues		2,088,000,000	3,169,000,000	4,335,000,000
Loss on disposals	[1]	(245,000,000)	0	(63,000,000)
Contingent consideration realized	[1]	27,000,000	21,000,000	47,000,000	[2]
Operating expenses
Vessel and rig operating expenses	[1]	792,000,000	1,015,000,000	1,611,000,000
Reimbursable expenses		35,000,000	61,000,000	99,000,000
Depreciation and amortization		798,000,000	810,000,000	779,000,000	[2]
Loss on impairment of long lived assets		696,000,000	44,000,000	563,000,000	[2]
General and administrative expenses	[1]	277,000,000	234,000,000	248,000,000
Total operating expenses		2,598,000,000	2,164,000,000	3,300,000,000
Operating (loss)/income		(728,000,000)	1,026,000,000	1,019,000,000
Financial items and other income/(expense), net
Interest income	[1]	60,000,000	66,000,000	67,000,000
Interest expense	[1]	(285,000,000)	(412,000,000)	(415,000,000)
Share in results from associated companies (net of tax)		174,000,000	283,000,000	192,000,000
Loss on impairment of investments		(841,000,000)	(895,000,000)	(1,285,000,000)
Gain/(loss) on derivative financial instruments	[1]	11,000,000	(74,000,000)	(150,000,000)
Net gain on debt extinguishment		19,000,000	47,000,000	8,000,000
Foreign exchange (loss)/gain		(65,000,000)	18,000,000	63,000,000
Gain on sale of tender rig business		0	0	22,000,000	[2]
Reorganization items, net		(1,337,000,000)	0	0
Other financial items and other (expense)/income, net	[1]	(44,000,000)	(15,000,000)	52,000,000
Total financial items and other (expense)/income, net		(2,308,000,000)	(982,000,000)	(1,446,000,000)
(Loss)/income before income taxes		(3,036,000,000)	44,000,000	(427,000,000)
Income tax expense		(66,000,000)	(199,000,000)	(208,000,000)
Net loss		(3,102,000,000)	(155,000,000)	(635,000,000)	[2],[3]
Net (loss)/income attributable to the non-controlling interest		(129,000,000)	26,000,000	(1,000,000)
Net loss attributable to the parent		$ (2,973,000,000)	$ (181,000,000)	$ (634,000,000)
Basic (loss)/earnings per share (in dollars per share)		$ (5.89)	$ (0.36)	$ (1.29)
Diluted (loss)/earnings per share (in dollars per share)		$ (5.89)	$ (0.36)	$ (1.29)
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".
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CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME / (LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	[2]
Statement of Comprehensive Income [Abstract]
Net loss	$ (3,102)	$ (155)	$ (635)	[1]
Other comprehensive income/(loss), net of tax:
Unrealized gain/(loss) on marketable securities, net	14	17	(460)
Actuarial (loss)/gain relating to pensions	(3)	22	27
Other than temporary impairment of marketable securities, reclassification to Statement of Operations	0	153	752
Unrealized foreign exchange differences	0	0	(15)
Other	2	1	0
Share of other comprehensive (loss)/income from associated companies	(8)	10	10
Other comprehensive income:	5	203	314
Total comprehensive (loss)/income for the period	(3,097)	48	(321)
Comprehensive (loss)/income attributable to the non-controlling interest	(121)	34	7
Comprehensive (loss)/income attributable to the parent	$ (2,976)	$ 14	$ (328)
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CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 1,255,000,000	$ 1,368,000,000
Restricted cash	104,000,000	75,000,000
Marketable securities	124,000,000	110,000,000
Accounts receivables, net	295,000,000	462,000,000
Amount due from related parties - current	217,000,000	376,000,000
Other current assets	257,000,000	495,000,000
Total current assets	2,252,000,000	2,886,000,000
Non-current assets
Investment in associated companies	1,473,000,000	2,168,000,000
Marketable securities	0	0
Newbuildings	248,000,000	1,531,000,000
Drilling units	13,216,000,000	14,276,000,000
Restricted cash	0	0
Deferred tax assets	10,000,000	12,000,000
Equipment	29,000,000	41,000,000
Amount due from related parties - non-current	547,000,000	523,000,000
Assets held for sale - non-current	126,000,000	128,000,000
Other non-current assets	81,000,000	101,000,000
Total non-current assets	15,730,000,000	18,780,000,000
Total assets	17,982,000,000	21,666,000,000
Current liabilities
Debt due within one year	509,000,000	3,195,000,000
Trade accounts payable	72,000,000	93,000,000
Amounts due to related parties - current	10,000,000	83,000,000
Other current liabilities	268,000,000	1,352,000,000
Total current liabilities	859,000,000	4,723,000,000
Liabilities Subject to Compromise	9,191,000,000	0
Non-current liabilities
Long-term debt	485,000,000	6,319,000,000
Long-term debt due to related parties	314,000,000	330,000,000
Deferred tax liabilities	107,000,000	112,000,000
Other non-current liabilities	67,000,000	119,000,000
Total non-current liabilities	973,000,000	6,880,000,000
Equity
Common shares of par value US$2.00 per share: 800,000,000 shares authorized 504,518,940 outstanding at December 31, 2017 (December 31, 2016, 504,444,280)	1,008,000,000	1,008,000,000
Additional paid in capital	3,313,000,000	3,306,000,000
Contributed surplus	1,956,000,000	1,956,000,000
Accumulated other comprehensive loss	58,000,000	53,000,000
Retained earnings	225,000,000	3,198,000,000
Total Shareholder’s equity	6,560,000,000	9,521,000,000
Non-controlling interest	399,000,000	542,000,000
Total equity	6,959,000,000	10,063,000,000
Total liabilities and equity	$ 17,982,000,000	$ 21,666,000,000

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2017	Sep. 12, 2017	Dec. 31, 2016	Jun. 30, 2016	Jun. 13, 2016	May 31, 2016	May 20, 2016	Dec. 31, 2015	May 10, 2005
Equity
Common shares, par value (in dollars per share)	$ 2		$ 2	$ 2		$ 2			$ 2
Common shares, shares authorized (in shares)	800,000,000		800,000,000					800,000,000
Common shares, shares outstanding (in shares)	504,518,940	508,763,020	504,444,280		508,444,280		500,944,280	492,759,940

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015	[1]
Cash Flows from Operating Activities
Net loss		$ (3,102)	$ (155)		$ (635)	[2]
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization		798	810		779
Amortization of deferred loan charges		27	45		39
Amortization of unfavorable and favorable contracts		(43)	(65)		(116)
Share of results from associated companies		(174)	(283)		(192)
Loss on disposal of drilling units		245	0		0
Share-based compensation expense		7	8		7
Loss on disposals and deconsolidations		0	0		63
Contingent consideration realized	[3]	(27)	(21)		(47)
Unrealized gain related to derivative financial instruments		(76)	(67)		(82)
Loss on impairment of long lived assets		696	44		563
Loss on impairment of investments		841	895		1,285
Gain on derecognition of investment in associated company		(10)	0		0
Dividends received from associated companies		39	55		253
Deferred income tax		7	73		29
Unrealized foreign exchange gain on long-term debt		59	(5)		(95)
Gain on sale of tender rig business		0	0		(22)
Payments for long-term maintenance		(58)	(95)		(106)
Net gain on debt extinguishment		(19)	(47)		(8)
Non-cash reorganization items, net of financing activities		1,274	0		0
Other		(2)	(2)		(9)
Changes in operating assets and liabilities, net of effect of acquisitions and disposals
Trade accounts receivable		167	256		267
Trade accounts payable		(9)	(55)		58
Related party receivables		(42)	2		65
Related party payables		(44)	(35)		(64)
Prepaid expenses/accrued revenue		(66)	15		(12)
Deferred revenue		(107)	(168)		(95)
Other assets		93	55		(22)
Other liabilities		(75)	(76)		(115)
Net cash provided by operating activities		399	1,184		1,788
Cash Flows from Investing Activities
Additions to newbuildings		(33)	(52)		(613)
Additions to drilling units and equipment		(59)	(84)		(322)
Refund of yard installments		25	53		29
Contingent consideration received		95	95		27
Settlement of West Mira		170	0		0
Sale of rigs and equipment		122	0		0
Buy out of guarantee		(28)	0		0
Sale of business, net of cash disposed		0	0		1,214
Change in restricted cash		(29)	(26)		(25)
Investment in associated companies		0	(16)		(210)
Loans granted to related parties		0	(120)		(523)
Payments received from loans granted to related parties		66	283		233
Proceeds from disposal of marketable securities		0	195		0
Net cash provided by/ (used in) investing activities		329	328		(190)
Cash Flows from Financing Activities
Proceeds from debt		0	0		1,516
Repayments of debt		(754)	(1,054)		(2,999)
Debt fees paid		(53)	(31)		(16)
Proceeds from debt to related party		0	0		143
Repayments of debt to related party		(39)	(103)		0
Dividends paid to non-controlling interests		0	(7)		(14)
Purchase of treasury shares		0	(10)		0
Cash settlement of restricted stock units		0	(1)		0
Net cash used in financing activities		(846)	(1,206)		(1,370)
Cash reclassified as held for sale		0	0		0
Effect of exchange rate changes on cash and cash equivalents		5	18		(15)
Net (decrease)/increase in cash and cash equivalents		(113)	324		213
Cash and cash equivalents at beginning of the year		1,368	1,044	[1]	831
Cash and cash equivalents at the end of year		1,255	1,368		1,044
Supplementary disclosure of cash flow information
Interest paid, net of capitalized interest		(264)	(400)		(458)
Taxes paid		$ (119)	$ (123)		$ (136)
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[3]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total		Total equity before NCI	Common shares	Additional paid in capital	Contributed surplus	Accumulated other comprehensive income/(loss)	Retained Earnings	Non-controlling interest
Beginning Balance, shares at Dec. 31, 2014				985,000,000
Beginning balance at Dec. 31, 2014	$ 10,390		$ 9,764		$ 3,258	$ 1,956	$ (448)	$ 4,013	$ 626
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale and purchase of treasury shares, net, shares				0
Sale of treasury shares	10		10		10
Share-based compensation charge	7		7		7
Sale of NCI	(4)								(4)
Other comprehensive income	314	[1]	306				306		8
Dividends declared	0		0					0	0
Distributions to non-controlling interests	(14)								(14)
Net (loss)/income	$ (635)	[1],[2]	(634)					(634)	(1)
Ending Balance, Shares at Dec. 31, 2015	492,759,940			985,000,000
Ending balance at Dec. 31, 2015	$ 10,068		9,453		3,275	1,956	(142)	3,379	615
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale and purchase of treasury shares, net, shares				(8,000,000)
Sale of treasury shares	(10)		(10)		(2)
Share-based compensation charge	7		7		7
Cash settlement of vested restricted stock units, shares				0
Cash settlement of vested restricted stock units	(1)		(1)		(1)
Conversion of convertible bond, shares				31,000,000
Conversion of convertible bond	58		58		27
Recognition of non-controlling interest	6								6
Other comprehensive income	203		195				195		8
Distributions to non-controlling interests	(113)								(113)
Net (loss)/income	$ (155)		(181)					(181)	26
Ending Balance, Shares at Dec. 31, 2016	504,444,280			1,008,000,000
Ending balance at Dec. 31, 2016	$ 10,063		9,521		3,306	1,956	53	3,198	542
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation charge	7		7		7
Other comprehensive income	5		5				5		0
Distributions to non-controlling interests	(14)								(14)
Net (loss)/income	$ (3,102)		(2,973)					(2,973)	(129)
Ending Balance, Shares at Dec. 31, 2017	504,518,940			1,008,000,000
Ending balance at Dec. 31, 2017	$ 6,959		$ 6,560		$ 3,313	$ 1,956	$ 58	$ 225	$ 399
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General information

General information	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General information	General information Seadrill Limited is incorporated in Bermuda and is a publicly listed company on the New York Stock Exchange and the Oslo Stock Exchange. We provide offshore drilling services to the oil and gas industry. As at December 31, 2017 we owned and operated 35 offshore drilling units, had 13 offshore drilling units under construction and an additional unit classified as held for sale. Seadrill's fleet consists of drillships, jack-up rigs and semi-submersible rigs for operations in shallow and deepwater areas, as well as benign and harsh environments. We also provide management services to our related parties Seadrill Partners and SeaMex, refer to Note 30 "Related party transactions" for further information. Basis of presentation The Consolidated Financial Statements are presented in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP). The amounts are presented in United States dollar ("U.S. dollar" or "US$") rounded to the nearest million, unless otherwise stated. The accompanying Consolidated Financial Statements present the financial position of Seadrill Limited, the consolidated subsidiaries and the group’s interest in associated entities. Investments in companies in which we control, or directly or indirectly holds more than 50% of the voting control are consolidated in the Consolidated Financial Statements, as well as certain variable interest entities of which we are deemed to be the primary beneficiary. Basis of consolidation The Consolidated Financial Statements include our assets and liabilities, our majority owned and controlled subsidiaries and certain variable interest entities, (“VIE”s) in which we are deemed to be the primary beneficiary. All intercompany balances and transactions have been eliminated on consolidation. A VIE is defined as a legal entity where either (a) the total equity at risk is not sufficient to permit the entity to finance its activities without additional subordinated support; (b) equity interest holders as a group lack either i) the power to direct the activities of the entity that most significantly impact on its economic success, ii) the obligation to absorb the expected losses of the entity, or iii) the right to receive the expected residual returns of the entity; or (c) the voting rights of some investors in the entity are not proportional to their economic interests and the activities of the entity involve or are conducted on behalf of an investor with a disproportionately small voting interest. U.S. GAAP requires a VIE to be consolidated by its primary beneficiary, being the interest holder, if any, which has both (1) the power to direct the activities of the entity which most significantly impact on the entity’s economic performance, and (2) the right to receive benefits or the obligation to absorb losses from the entity which could potentially be significant to the entity. We evaluate our subsidiaries, and any other entities in which we hold a variable interest, in order to determine whether we are the primary beneficiary of the entity, and where it is determined that we are the primary beneficiary we consolidate the entity. Investment in companies in which we exercises significant influence, but do not consolidate, are accounted for using the equity method and classified within “Investments in associated companies.” We record our share of earnings or losses from associated companies in the Consolidated Statements of Operations as “Share in results from associated companies.” The excess, if any, of purchase price over book value of our investments in equity method investees is included in the accompanying consolidated balance sheets in “Investment in associated companies.” Investments in companies in which our ownership is less than 20% are valued at fair value and classified within “Marketable Securities” unless it is not possible to estimate fair value, then the cost method is used. Bankruptcy accounting Seadrill Limited and certain of its direct and indirect consolidated subsidiaries (the “Debtors”) filed voluntary petitions on September 12, 2017 (the "Petition Date") to commence prearranged reorganization proceedings under Chapter 11 of Title 11 of the United States Bankruptcy Code (“Bankruptcy Code”) in the Southern District of Texas (the “Bankruptcy Court”) [case number 17-60079]. The Debtors also commenced a provisional liquidation proceeding in Bermuda on behalf of the Bermudian entities. During the pendency of the Chapter 11 proceedings, the Debtors will operate its business as “debtor-in-possession” under the jurisdiction of the Bankruptcy Court and in accordance with the applicable provision of the Bankruptcy Code. Read Note 3 for a discussion of the Chapter 11 proceedings. The consolidated financial statements have been prepared as if we are a going concern and reflect the application of Accounting Standards Codification 852, Reorganizations ("ASC 852") . ASC 852 requires that the financial statements, for periods subsequent to filing bankruptcy petitions, distinguish transactions and events that are directly associated with the reorganization from the ongoing operations of the business. Accordingly, certain expenses, gains and losses that are realized or incurred in the bankruptcy proceedings are recorded in “Reorganization items, net" on the Company’s Consolidated Statements of Operations. In addition, ASC 852 provides for changes in the accounting and presentation of significant items on the consolidated balance sheets, particularly liabilities. Pre-petition obligations that may be impacted by the Chapter 11 reorganization process have been classified on the consolidated balance sheets in liabilities subject to compromise. These liabilities are reported at the amounts expected to be allowed by the Bankruptcy Court, even if they may be settled for lesser amounts. If we emerge from bankruptcy, we will assess the criteria for applying fresh start accounting. If the criteria are met, we will apply fresh start accounting and record our assets and liabilities at fair value as of the fresh start reporting date. The fair value of our assets and liabilities as of that date may differ materially from the recorded values of our assets and liabilities as reflected in our historical Consolidated Financial Statements. In addition, the adoption of fresh start accounting may materially affect the results of operations following the fresh-start reporting date, as we will have a new basis in our assets and liabilities. Consequently, our historical financial statements would not be reliable indicators of our financial condition and results of operations for any period should we apply fresh start accounting. Going Concern Our consolidated financial statements have been prepared on a going concern basis and contemplate the realization of assets and satisfaction of liabilities in the normal course of business. Our going concern assumption is based on management’s expectation that the current restructuring program described in Note 3 "Chapter 11 Proceedings" will alleviate the primary conditions that raise substantial doubt as to our ability to continue as a going concern when completed. Furthermore, our business operations are unaffected by the Chapter 11 Proceedings and the restructuring efforts, and we expect to meet our ongoing customer and business counterparty obligations during the course of the proceedings. We have been engaged in discussions with our banks, potential new investors, existing stakeholders and bondholders in order to restructure our secured credit facilities and unsecured liabilities and recapitalize our balance sheet with new capital. These collaborative efforts resulted in the signing of a Restructuring Support and Lock-Up Agreement (“RSA”) on September 12, 2017, subsequently amended on February 26, 2018, which provides for several conditions to be met in order to fully effectuate the intended restructuring. Although we anticipate that our restructuring plan will address our liquidity concerns, uncertainty remains over the bankruptcy court's approval of our plan of reorganization, and therefore substantial doubt exists over our ability to continue as a going concern for twelve months after the date the financial statement are issued. To the extent the Plan is confirmed, and we emerge from Chapter 11,we expect this substantial doubt to be mitigated. The consolidated financial statements do not include any adjustments that might result from the outcome of the going concern uncertainty. Upon emergence from Chapter 11 proceedings adjustments to the carrying values and classifications of our assets and liabilities and the reported amounts of income and expenses could be required that may be material. For further details of management’s plan to alleviate substantial doubt relating to going concern, refer to Note 3 "Chapter 11 Proceedings".

Accounting policies

Accounting policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Accounting policies	Accounting policies The accounting policies set out below have been applied consistently to all periods in these consolidated financial statements, unless otherwise noted. Use of estimates Preparation of financial statements in accordance with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Contract revenue A substantial majority of our revenues are derived from dayrate based drilling contracts and other service contracts. We recognize dayrate revenues ratably over the contract period when services are rendered. Under some contracts, we are entitled to additional payments for meeting or exceeding certain performance targets. Such additional payments are recognized when any contingencies are resolved or upon completion of the drilling program. We may receive lump sum fees for the mobilization of equipment and personnel or for capital additions and upgrades prior to commencement of drilling services. These up-front fees are recognized as revenue over the expected contract term. We may also receive fees for making capital upgrades during the contract. We recognize revenue for such fees over the expected remaining contract term. In some cases, we may receive lump sum fees or dayrate based fees from customers for demobilization upon completion of a drilling contract. We recognize non-contingent demobilization fees as revenue over the expected contract term. We recognize revenue for contingent demobilization fees as earned upon completion of the drilling contract. In some countries, the local government or taxing authority may assess taxes on our revenues. Such taxes may include sales taxes, use taxes, value-added taxes, gross receipts taxes and excise taxes. We generally record tax-assessed revenue transactions on a net basis. Reimbursable revenue and expenses Reimbursements received for the purchases of supplies, personnel services and other services provided on behalf of and at the request of our customers in accordance with a contract or agreement are recorded as revenue. The related costs are recorded as reimbursable expenses in the same period. Other revenues In a business combination there may exist unfavorable drilling contracts which are recorded at fair value at the date of acquisition. An unfavorable drilling contract is a contract that has a dayrate which differs from prevailing market rates at the time of acquisition. The net present values of such contracts are recorded as a liability at the purchase date and subsequently recognized as revenue over the contract term. Related party revenues relate to management support and administrative services provided to Seadrill Partners and SeaMex. External management fees relate to the operational, administrative and support services provided to third parties. Other revenues also include amounts recognized as early termination fees under drilling contracts which have been terminated prior to the contract end date. Contract termination fees are recognized daily as and when any contingencies or uncertainties are resolved. Mobilization and demobilization expenses We incur costs to prepare a drilling unit for a new customer contract and to move the rig to the contract location. We recognize the expense for such mobilization costs over the expected contract term. We incur costs to transfer a drilling unit to a safe harbor or different geographic area at the end of a contract. We expense such demobilization costs as incurred. We also expense any costs incurred to relocate drilling units that are not under contract. Vessel and Rig Operating Expenses Vessel and rig operating expenses are costs associated with operating a drilling unit that is either in operation or stacked, and include the remuneration of offshore crews and related costs, rig supplies, insurance costs, expenses for repairs and maintenance and costs for onshore support personnel. We expense such costs as incurred. Repairs, maintenance and periodic surveys Costs related to periodic overhauls of drilling units are capitalized and amortized over the anticipated period between overhauls, which is generally five years. Related costs are primarily yard costs and the cost of employees directly involved in the work. We include amortization costs for periodic overhauls in depreciation and amortization expense. Costs for other repair and maintenance activities are included in vessel and rig operating expenses and are expensed as incurred. Foreign currencies Seadrill Limited and the majority of our subsidiaries use U.S. dollars as the functional currency because the majority of our revenues and expenses are denominated in U.S. dollars. Accordingly, our reporting currency is also U.S. dollars. For subsidiaries that maintain their accounts in currencies other than U.S. dollars, we use the current method of translation whereby the Statement of Operations are translated using the average exchange rate for the year and the assets and liabilities are translated using the year-end exchange rate. Foreign currency translation gains or losses on consolidation are recorded as a separate component of other comprehensive income in shareholders' equity. Transactions in foreign currencies are translated into U.S. dollars at the rates of exchange in effect at the date of the transaction. Foreign currency assets and liabilities are translated using rates of exchange at the balance sheet date. Gains and losses on foreign currency transactions are included in the Consolidated Statements of Operations. Current and non-current classification Assets and liabilities (excluding deferred taxes) are classified as current assets and liabilities respectively, if their maturity is within one year of the balance sheet date. Otherwise, they are classified as non-current assets and liabilities. Cash and cash equivalents Cash and cash equivalents consist of cash, bank deposits and highly liquid financial instruments with maturities of three months or less. Restricted cash Restricted cash consists of bank deposits which have been pledged as collateral for certain guarantees issued by a bank or minimum deposits which must be maintained in accordance with contractual arrangements. Restricted cash amounts with maturities longer than one year are classified as non-current assets. Equity method investments Investments in common stock are accounted for using the equity method of accounting if the investment gives us the ability to exercise significant influence, but not control over, the investee. Significant influence is generally deemed to exist if our ownership interest in the voting stock of the investee is between 20% and 50%, although other factors such as representation on the investee’s Board of Directors and the nature of commercial arrangements are also considered. Under the equity method of accounting, we record investments in equity-method investees in the consolidated balance sheet under “Investment in associated companies” and our share of the investees’ earnings or losses together with other-than-temporary impairments in value and gain/loss on sale of investments under “Share in results from associated companies (net of tax)” in the consolidated statements of income. All other equity investments, which consist of investments that do not gives us the ability to exercise significant influence as well as investments in equity instruments other than common stock, are accounted for under the cost method or at fair value, if readily determinable. We analyze our equity method investments for impairment at each reporting period to evaluate whether an event or change in circumstances has occurred in that period that may have a significant adverse effect on the value of the investment. We record an impairment charge for other-than-temporary declines in value when the value is not anticipated to recover above the cost within a reasonable period after the measurement date, unless there are mitigating factors that indicate impairment may not be required. If an impairment charge is recorded, subsequent recoveries in value are not reflected in earnings until sale of the equity method investee occurs. Marketable securities Marketable equity securities which do not give us the ability to exercise significant influence are classified as available-for-sale. These are remeasured at fair value each reporting period with resulting unrealized gains and losses recorded as a separate component of accumulated other comprehensive income in shareholders’ equity. Gains and losses are not realized until the securities are sold or subject to an other than temporary impairment. Gains and losses on forward contracts to purchase marketable equity securities that do not meet the definition of a derivative are accounted for as available-for-sale. We analyze our available-for-sale securities for impairment at each reporting period to evaluate whether an event or change in circumstances has occurred in that period that may have a significant adverse effect on the value of the securities. We record an impairment charge for other-than-temporary declines in value when the value is not anticipated to recover above the cost within a reasonable period after the measurement date, unless there are mitigating factors that indicate impairment may not be required. If an impairment charge is recorded, subsequent recoveries in value are not reflected in earnings until sale of the securities held as available for sale occurs. Receivables Receivables, including accounts receivable, are recorded in the balance sheet at their nominal amount less an allowance for doubtful accounts. We establish reserves for doubtful accounts on a case-by-case basis when it is unlikely that required payments of specific amounts will occur. In establishing these reserves, we consider the financial condition of the customer as well as specific circumstances related to the receivable such as customer disputes. Receivable amounts determined as being unrecoverable are written off. Newbuildings The carrying value of drilling units under construction (“Newbuildings”) represents the accumulated costs at the balance sheet date. Cost components include payments for yard installments and variation orders, construction supervision, equipment, spare parts, capitalized interest, costs related to first time mobilization and commissioning costs. No charge for depreciation is made until commissioning of the newbuilding has been completed and it is ready for its intended use. We may have option agreements with shipyards to order new drilling units at fixed or variable prices which require some or no additional payment upon exercise. Payments for drilling unit purchase options are capitalized at the time when option contracts are acquired or entered into. We review the expected future cash flows, which would result from the exercise of each option contract on a contract by contract basis to determine whether the carrying value of the option is recoverable. Newbuildings are evaluated for impairment according to the impairment of long-lived assets accounting policy described below. Capitalized interest Interest expense is capitalized during construction of newbuildings based on accumulated expenditures for the applicable project at our current rate of borrowing. The amount of interest expense capitalized in an accounting period shall be determined by applying an interest rate (“the capitalization rate”) to the average amount of accumulated expenditures for the asset during the period. The capitalization rates used in an accounting period shall be based on the rates applicable to borrowings outstanding during the period. We don't capitalize amounts beyond the actual interest expense incurred in the period. If our financing plans associate a specific loan with a qualifying asset, we use the rate on that loan as the capitalization rate to be applied to that portion of the average accumulated expenditures for the asset, provided that his amount does not exceed the amount of the loan. If average accumulated expenditures for the asset exceed the amounts of loans associated with the asset, the capitalization rate to be applied to such excess shall be a weighted average of the rates applicable to our other loans. During Chapter 11 no interest on newbuildings has been capitalized as interest payments made during bankruptcy proceedings are treated as adequate protection payments. Drilling units Rigs, vessels and related equipment are recorded at historical cost less accumulated depreciation. The cost of these assets, less estimated residual value is depreciated on a straight-line basis over their estimated remaining economic useful lives. The estimated residual value is taken to be offset by any decommissioning costs that may be incurred. The estimated economic useful life of our floaters and, jack-up rigs, when new, is 30 years. Significant investments are capitalized and depreciated in accordance with the nature of the investment. Significant investments that are deemed to increase an asset’s value for its remaining useful life are capitalized and depreciated over the remaining life of the asset. Drilling units that are acquired in business combinations are recognized at fair value on date of acquisition. Cost of property and equipment sold or retired, with the related accumulated depreciation and write-downs are removed from the consolidated balance sheet, and resulting gains or losses are included in the consolidated statement of operations. Assets held for sale Assets are classified as held for sale when all of the following criteria are met: Management, having the authority to approve the action, commits to a plan to sell the asset (disposal group), the asset is available for immediate sale in its present condition subject only to terms that are usual and customary for sales of such assets, an active program to locate a buyer and other actions required to complete the plan to sell the asset (disposal group) have been initiated, the sale of the asset is probable, and transfer of the asset is expected to qualify for recognition as a completed sale, within 1 year. The term probable refers to a future sale that is likely to occur, the asset is being actively marketed for sale at a price that is reasonable in relation to its current fair value and actions required to complete the plan indicate that it is unlikely that significant changes to the plan will be made or that the plan will be withdrawn. Discontinued operations If the disposal of a component represents a strategic shift that has had (or will have) a major effect on our operations and financial results, then we present the results of that component as discontinued, provided that the component has either been disposed of or is classified as held for sale at the reporting date. Equipment Equipment is recorded at historical cost less accumulated depreciation and is depreciated over its estimated remaining useful life. The estimated economic useful life of equipment, when new, is between 3 and 5 years depending on the type of asset. Other intangible assets and liabilities Other intangible assets and liabilities are recorded at fair value on the date of acquisition less accumulated amortization. The amounts of these assets and liabilities less the estimated residual value, if any, is generally amortized on a straight-line basis over the estimated remaining economic useful life or contractual period. Other intangible assets include technology, customer relationships and favorable drilling contracts. Other intangible liabilities include unfavorable drilling contracts. Impairment of long-lived assets We review the carrying value of our long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may no longer be appropriate. We first assess recoverability of the carrying value of the asset by estimating the undiscounted future net cash flows expected to result from the asset, including eventual disposal. If the undiscounted future net cash flows are less than the carrying value of the asset, we then compare the carrying value of the intangible asset with the discounted future net cash flows, using relevant WACC to determine an impairment loss to be recognized during the period. Defined benefit pension plans We have several defined benefit plans which provide retirement, death and early termination benefits. Our net obligation is calculated separately for each plan by estimating the amount of the future benefit that employees have earned in return for their cumulative service. The aggregated projected future benefit obligation is discounted to a present value, and the aggregated fair value of any plan assets is deducted. The discount rate is the market yield at the balance sheet date on government bonds in the relevant currency and based on terms consistent with the post-employment benefit obligations. The retirement benefits are generally a function of number of years of employment and amount of employees’ remuneration. The plans are primarily funded through payments to insurance companies. We record pension costs in the period during which the services are rendered by the employees. Actuarial gains and losses are recognized in the Statement of Operations when the net cumulative unrecognized actuarial gains or losses for each individual plan at the end of the previous reporting year exceed 10 percent of the higher of the present value of the defined benefit obligation and the fair value of plan assets at that date. These gains and losses are recognized over the expected remaining working lives of the employees participating in the plans. Otherwise, recognition of actuarial gains and losses is included in other comprehensive income. Those amounts will be subsequently recognized as a component of net periodic pension cost on the same basis as the amounts recognized in accumulated other comprehensive income. On retirement, or when an employee leaves the company, the member’s pension liability is transferred to the life insurance company administering the plan, and the pension plan no longer retains an obligation relating to the leaving member. This action is deemed to represent a settlement under U.S. GAAP, as it represents the elimination of significant risks relating to the pension obligation and related assets. Under settlement accounting U.S. GAAP requires a portion of the net unrealized actuarial gains/losses to be recognized through the Statement of Operations. The portion corresponds to the relative value of the obligation reduction as a result of the settlement. However, settlement accounting is not required if the cost of all settlements in a year is not deemed to be significant in the context of the plan. We deem the settlement not to be significant when the cost of settlements in the year is less than the sum of service cost and interest cost in the year. In this case the difference between the reduction in benefit obligation and the plan assets transferred to the life insurance company is recognized within “other comprehensive income,” rather than being recognized in the Statement of Operations. Treasury shares Treasury shares are recognized at cost as a component of equity. We record the nominal value of treasury shares purchased as a reduction in share capital. The amount paid in excess of the nominal value is treated as a reduction of additional paid-in capital. Derivative Financial Instruments and Hedging Activities Historically, our main derivative instruments included interest-rate swap agreements, foreign currency options and forward exchange contracts which were recorded at fair value. Changes in the fair value of derivatives, which have not been designated as hedging instruments, are recorded as a gain or loss as a separate line item within "financial items" in the Consolidated Statements of Operations. Changes in the fair value of any derivative instrument that has been formally designated as a hedge, are recognized in "Accumulated other comprehensive income" in the Consolidated Balance Sheets. Any change in fair value relating to an ineffective portion of a designated hedge is recognized, in the Consolidated Statements of Operations. When the hedged item affects the income statement, the gain or loss included in Accumulated other comprehensive income is reported on the same line in the consolidated statements of operations as the hedged item. Income taxes Seadrill is a Bermuda company that has subsidiaries and affiliates in various jurisdictions. Currently, Seadrill and our Bermudan subsidiaries and affiliates are not required to pay taxes in Bermuda on ordinary income or capital gains as they qualify as exempt companies. Seadrill and our subsidiaries and affiliates have received written assurance from the Minister of Finance in Bermuda that we will be exempt from taxation until March 2035. Certain subsidiaries operate in other jurisdictions where taxes are imposed. Consequently, income taxes have been recorded in these jurisdictions when appropriate. Our income tax expense is based on our income and statutory tax rates in the various jurisdictions in which we operate. We provide for income taxes based on the tax laws and rates in effect in the countries in which operations are conducted and income is earned. The determination and evaluation of our annual group income tax provision involves interpretation of tax laws in various jurisdictions in which we operate and requires significant judgment and use of estimates and assumptions regarding significant future events, such as amounts, timing and character of income, deductions and tax credits. There are certain transactions for which the ultimate tax determination is unclear due to uncertainty in the ordinary course of business. We recognize tax liabilities based on our assessment of whether our tax positions are more likely than not sustainable, based solely on the technical merits and considerations of the relevant taxing authorities widely understood administrative practices and precedence. Changes in tax laws, regulations, agreements, treaties, foreign currency exchange restrictions or our levels of operations or profitability in each jurisdiction may impact our tax liability in any given year. While our annual tax provision is based on the information available to us at the time, a number of years may elapse before the ultimate tax liabilities in certain tax jurisdictions are determined. Current income tax expense reflects an estimate of our income tax liability for the current year, withholding taxes, changes in prior year tax estimates as tax returns are filed, or from tax audit adjustments. Income tax expense consists of taxes currently payable and changes in deferred tax assets and liabilities calculated according to local tax rules. Deferred tax assets and liabilities are based on temporary differences that arise between carrying values used for financial reporting purposes and amounts used for taxation purposes of assets and liabilities and the future tax benefits of tax loss carry forwards. Our deferred tax expense or benefit represents the change in the balance of deferred tax assets or liabilities as reflected on the balance sheet. Valuation allowances are determined to reduce deferred tax assets when it is more likely than not that some portion or all of the deferred tax assets will not be realized. To determine the amount of deferred tax assets and liabilities, as well as at the Valuation allowances, we must make estimates and certain assumptions regarding future taxable income, including where our drilling units are expected to be deployed, as well as other assumptions related to our future tax position. A change in such estimates and assumptions, along with any changes in tax laws, could require us to adjust the deferred tax assets, liabilities, or valuation allowances. The amount of deferred tax provided is based upon the expected manner of settlement of the carrying amount of assets and liabilities, using tax rates enacted at the balance sheet date. The impact of tax law changes is recognized in periods when the change is enacted. Deferred charges Loan related costs, including debt issuance, arrangement fees and legal expenses, are capitalized and presented in the balance sheet as a direct deduction from the carrying amount of the related debt liability, and amortized over the term of the related loan and the amortization is included in interest expense. Convertible debt Convertible bond loans include both a loan component (host contract) and an option to convert the loan to shares (embedded derivative). An embedded derivative, such as a conversion option, may be separated from its host contract and accounted for separately if certain criteria are met (including if the contract that embodies both the embedded derivative and the host contract is not measured at fair value, the economic characteristics and risks of the embedded derivative instrument are not clearly and closely related to the economic characteristics and risks of the host contract and if a separate instrument with the same terms as the embedded instrument would be a derivative). If an embedded derivative instrument is separated from its host contract, the host contract shall be accounted for based on generally accepted accounting principles applicable to instruments of that type which do not contain embedded derivative instruments. Total Return Equity Swaps From time to time, we enter into total return equity swaps (“TRS”) indexed to our own shares. Under such arrangements, the counterparty acquires shares in Seadrill and we carry the risk of fluctuations in the market price of those shares. The fair value of each TRS is recorded as an asset or liability, with the changes in fair value recorded in the consolidated statement of operations. We may, from time to time, enter into TRS arrangements indexed to shares in other companies which are accounted for in a similar manner. Share-based compensation We have an employee share ownership plan under which our employees, directors and officers may be allocated options to subscribe for new shares in the ultimate parent, Seadrill Limited. The compensation cost for share options is recognized as an expense over the service period based on the fair value of the options granted. The fair value of the share options issued under employee share option plans is determined at grant date taking into account the terms and conditions upon which the options are granted, and using a valuation technique that is consistent with generally accepted valuation methodologies for pricing financial instruments, and that incorporates all factors and assumptions that knowledgeable, willing market participants would consider in determining fair value. The fair value of the share options is recognized as personnel expenses with a corresponding increase in equity over the period during which the employees become unconditionally entitled to the options. Compensation cost is initially recognized based upon options expected to vest with appropriate adjustments to reflect actual forfeitures. National insurance contributions arising from such incentive programs are expensed when the options are exercised. We also have a Restricted Stock Unit(“RSU”) plan where the holder of an award is entitled to receive shares if still employed at the end of the three -year vesting period. There is no requirement for the holder to pay for the share on grant or vesting of the award. The fair value of the RSU award is calculated as the market share price on grant date. The fair value of the awards expected to vest is recognized as compensation cost straight-line over the vesting period. Loss contingencies We recognize a loss contingency in the consolidated balance sheet where we have a present legal or constructive obligation as a result of a past event, and it is probable that an outflow of economic benefits will be required to settle the obligation and a reliable estimate of the amount can be made. If the effect is material, provisions are determined by discounting the expected future cash flows at a pre-tax rate that reflects current market assessments of the time value of money and, where appropriate, the risks specific to the liability. Related parties Parties are related if one party has the ability, directly or indirectly, to control the other party or exercise significant influence over the other party in making financial and operating decisions. Parties are also related if they are subject to common control or common significant influence. Earnings per share Basic earnings per share (“EPS”) is calculated based on the income/(loss) for the period available to common stockholders divided by the weighted average number of shares outstanding for basic EPS for the period. Diluted EPS includes the effect of the assumed conversion of potentially dilutive instruments. This includes share options, restricted stock units and convertible debt. The determination of dilutive earnings per share may require us to make adjustments to net income and the weighted average shares outstanding. Recently Adopted Accounting Standards We adopted the following accounting standard updates ("ASUs") in the year, none of which had any impact on our consolidated financial statements and related disclosures: • ASU 2016-05 - Derivatives and Hedging (Topic 815): Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships (a consensus of the Emerging Issues Task Force) • ASU 2016-06 - Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the Emerging Issues Task Force) • ASU 2016-07 - Investments—Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting • ASU 2016-09 - Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting • ASU 2016-17 - Consolidation (Topic 810): Interests Held through Related Parties that are under Common Control • ASU 2016-19 - Technical Corrections and Improvements Recently Issued Accounting Standards The FASB have issued the following ASUs that we have not yet adopted but which could affect our consolidated financial statements and related disclosures in future periods. • ASU 2014-09 - Revenue from Contracts with Customers (also 2016-8, 2016-10, 2016-11, 2016-12, 2016-20, 2017-13, 2017-14) • ASU 2016-01 - Financial Instruments — Recognition and Measurement of Financial Assets and Financial Liabilities • ASU 2016-02 - Leases • ASU 2016-13 - Financial Instruments — Measurement of Credit Losses on Financial Instruments • ASU 2016-15 - Statement of Cash Flows — Classification of Certain Cash Receipts and Cash Payments • ASU 2016-16 - Income taxes — Intra-Entity Transfers of Assets other than Inventory • ASU 2016-18 - Statement of Cash Flows — Restricted Cash • ASU 2017-01 - Business Combinations — Clarifying the Definition of a Business • ASU 2017-04 - Intangibles — Simplifying the Test for Goodwill Impairment • ASU 2017-05 - Other Income—Gains and Losses from the Derecognition of Nonfinancial Assets ASU 2014-09 - Revenue from contracts with customer ASU 2014-09 - Revenue from contracts with customers In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers , which provides new authoritative guidance on the methods of revenue recognition and related disclosure requirements. This new standard supersedes all existing revenue recognition requirements, including most industry-specific guidance. We will be required to apply this standard for the year ended December 31, 2018 and for interim periods within that year. We have substantially completed our work to implement the new standard and do not expect our pattern of revenue recognition to materially change as a consequence of adopting the new guidance. We plan to use the modified retrospective method to transition to the new standard. This method requires us to apply the new standard to all outstanding contracts as of January 1, 2018. Under this method we record the cumulative effect of applying the new standard as an adjustment to opening retained earnings. To apply the standard, we were required to assess the core promise made to our customers under a drilling contract. We have assessed that our core promise is to stand ready to provi

Chapter 11 Proceedings (Notes)

Chapter 11 Proceedings (Notes)	12 Months Ended
	Dec. 31, 2017
Reorganizations [Abstract]
Reorganization under Chapter 11 of US Bankruptcy Code Disclosure [Text Block]	Proceedings Restructuring Support Agreement and Bankruptcy Proceedings under Chapter 11 Over the past two years we have been engaged in extensive discussions with our secured lenders and potential new money investors regarding the terms of a comprehensive restructuring. These discussions have also included an ad hoc committee of bondholders and other creditors including several of our newbuild shipyards. The objectives of our restructuring are to build a bridge to a recovery and achieve a sustainable capital structure. We have proposed to achieve this by extending bank maturities, reducing fixed amortization, amending financial covenants and raising new capital. On April 4, 2017 we reac hed an agreement with our banking group of secured lenders to extend the comprehensive restructuring plan negotiating period until July 31, 2017. Further we agreed to extend the related covenant amendments and waivers expiring on June 30, 2017 to September 30, 2017 and received lender consent to extend the maturity dates of certain facilities falling due within that period. This provided us with additional time to advance ongoing negotiations regarding the terms of a comprehensive restructuring plan. During April 2017 as part of our restructuring plans we signed and closed an agreement with Archer and its lenders to extinguish approximately $253 million in financial guarantees provided by us in exchange for a cash payment of approximately $25 million . In June 2017 we signed and closed a further agreement with Archer and its lenders to extinguish the remaining $25 million of financial guarantees in exchange for a cash payment of approximately $3 million . In July 2017, we reached an agreement with our secured lender bank group to further extend the date by which a comprehensive restructuring plan must be agreed until September 12, 2017 providing an additional period for negotiations to continue over a comprehensive restructuring plan. We also extended the maturities of its $400 million credit facility and the $450 million credit facility provided to Seadrill Eminence Ltd. to September 14, 2017. The $440 million facility provided to Seadrill Eminence Ltd. was further amended in August 2017 by way of a scheme of arrangement under section 99 of the Companies Act 1981 of Bermuda to align the maturity of the facility with that of (i) our $400 million credit facility and (ii) the revolving credit facility provided to NADL. In August 2017 we completed amendments to three secured credit facilities that relate to rigs purchased by Seadrill Partners from us that insulated Seadrill Partners from events of default related to our likely use of in-court processes, including Chapter 11 proceedings, to implement a restructuring plan. The amendments to the three facilities removed Seadrill Partners and its consolidated entities as a borrower or guarantor and separated the facilities such that each resulting Seadrill Limited facility is secured only by Seadrill Limited's assets without recourse to Seadrill Partners or its assets. On September 12, 2017, we entered into a restructuring support and lock-up agreement with a group of senior secured bank lenders, unsecured bondholders, certain other stakeholders and new-money providers (collectively, the “Consenting Stakeholders”). Our consolidated subsidiaries North Atlantic Drilling Ltd. (“NADL”) and Sevan Drilling Limited (“Sevan”), together with certain other of our consolidated subsidiaries also entered into the RSA (collectively with Seadrill, the “Company Parties”). Ship Finance International Limited and three of its subsidiaries (“SFL”), which charter three drilling units to the Company Parties, also executed the RSA. In connection with the RSA, the Company Parties entered into an investment agreement (the “Investment Agreement”) under which Hemen Investments Limited (“Hemen”), an affiliate of Seadrill’s largest shareholder Hemen Holding Ltd. and a consortium of investors, including the bondholder parties to the RSA (collectively, the “Commitment Parties”), committed to provide $1.06 billion in new cash commitments, subject to certain terms and conditions (the “Capital Commitment”). Our non-consolidated affiliates, including Seadrill Partners LLC, SeaMex Ltd., Archer Limited, and their respective subsidiaries, did not commence proceedings under Chapter 11 and are not parties to the RSA or Investment Agreement. We expect their business operations to continue uninterrupted. On September 12, 2017, to implement the transactions contemplated by the RSA and Investment Agreement, Seadrill and the other Company Parties (collectively, the “Debtors”) commenced prearranged reorganization proceedings under Chapter 11 of title XI of the United States Code in the Southern District of Texas (the “Bankruptcy Court”) [case number 17-60079]. During the course of the bankruptcy proceedings, the Debtors continue to operate their business as a debtor in possession. On the Petition Date, the Bankruptcy Court issued certain additional customary interim and final orders with respect to the Debtors’ first day motions and other operating motions that allow the Debtors to operate their businesses in the ordinary course. The first-day motions provided for, among other things, the payment of certain pre-petition employee and retiree expenses and benefits, the use of the Debtors’ existing cash management system, the payment of certain pre-petition amounts to certain critical vendors, the ability to pay certain pre-petition taxes and regulatory fees, the payment of certain pre-petition claims owed on account of insurance policies and programs and authorizing the use of cash collateral. Concurrent with the commencement of the prearranged reorganization proceedings in the Bankruptcy Court, Seadrill, NADL and Sevan (collectively, the “Bermuda Debtors”) commenced provisional liquidation proceedings pursuant to section 161 and 170 of the Bermuda Companies Act 1981 by presenting “winding up” petitions to the Bermuda Court. Upon the application of the Bermuda Debtors, the Bermuda Court appointed three joint provisional liquidators for each of the Bermuda Debtors. Under the order appoint the joint provisional liquidators, the joint provisional liquidators’ powers are limited such that the Bermuda Debtors’ management team and boards of directors remain in control of the Bermuda Debtors’ day-to-day operations. Upon the appointment of the joint provisional liquidators in respect to each of the Bermuda Debtors, a statutory stay of proceedings in Bermuda against those three entities or their assets automatically arose. The next hearing in the Bermuda Court with respect to the “winding up” petitions was set for April 27, 2018. In addition to the statutory stay, as soon as practicable following the effective date (in accordance with the Plan of Reorganization), the provisional liquidators’ Bermuda law counsel, with the support of the Debtors, will apply for winding up orders in respect of each of the Bermuda Debtors. The joint provisional liquidators will also seek formal recognition of the Confirmation Order from the United States Bankruptcy Court in Bermuda. On February 26, 2018 the Debtors filed a second amended joint Chapter 11 plan of reorganization, amended disclosure statement, amendment to the RSA, and amendment to the investment agreement. The amendments were the result of the Debtors reaching a global settlement with the Consenting Stakeholders and certain newbuild counterparties whereby certain creditor parties were included as Commitment Parties to the Investment Agreement, the size of the new cash infusion of the Investment Agreement increased from $1.06 billion to $1.08 billion , certain cash pools were established for the benefit of various creditor groups and also for the fees and expenses of their advisors, immediate cessation of all litigation and discovery efforts on the part of the creditor groups and committees was agreed, and a three -month extension to the maturities of the senior credit facilities under the original terms of the RSA was agreed. The RSA may be terminated upon the occurrence of certain events, including the failure to meet specified milestones relating to the filing, confirmation, and consummation of the Plan, among other requirements, and in the event of certain breaches by the parties under the RSA. The RSA is subject to termination if the effective date of the Plan has not occurred within 11 months of the Petition Date. As a result, there is no assurance the confirmation and effectiveness of the Plan contemplated in the RSA will occur. Plan of Reorganization Consistent with the RSA, the Debtors filed a proposed plan of reorganization and disclosure statement with the Bankruptcy Court on September 12, 2017, as well as a disclosure statement relating to the proposed plan of reorganization. Subsequent to September 12, 2017, the Debtors negotiated with its various creditors, including an ad hoc group of holders of unsecured bonds (the “Ad Hoc Group”) and ship yards with which the Debtors had a contractual relationship to build new rigs. On February 26, 2018, the Debtors announced a global settlement with the Ad Hoc Group, the official committee of unsecured creditors (the “Committee”) and other major creditors in its Chapter 11 cases, including Samsung Heavy Industries Co., Ltd. and Daewoo Shipbuilding & Marine Engineering Co., Ltd., two of the Debtors’ newbuild shipyards, and an affiliate of Barclays Bank PLC (“Barclays”), another holder of unsecured bonds. In connection with the global settlement, the Debtors entered into an amendment to the RSA and an amendment to the Investment Agreement. The amendments to the RSA and Investment Agreement provided for the inclusion of the Ad Hoc Group and Barclays into the Capital Commitment as Commitment Parties, increased recoveries for general unsecured creditors of Seadrill, NADL, and Sevan under the plan of reorganization, an agreement regarding the allowed claim of the newbuild shipyards and an immediate cessation of all litigation and discovery efforts in relation to the plan of reorganization. The Investment Agreement, as amended, provides for certain milestones for the Debtors’ restructuring: (1) the Bankruptcy Court must enter an order confirming the Plan by June 9, 2018 (the “Confirmation Date”) and (2) the effective date of the Plan must occur within 90 days of the Confirmation Date and, in any event, no later than August 8, 2018. In connection with the global settlement, on February 26, 2018, the Debtors filed a proposed Second Amended Joint Chapter 11 Plan of Reorganization with the Bankruptcy Court (the “Plan”). On February 26, 2018, the Bankruptcy Court entered an order approving (i) the adequacy of the Disclosure Statement, (ii) the solicitation and notice procedures with respect to confirmation of the Debtors’ proposed Plan, (iii) the rights offering procedures for the rights offerings contemplated by the Plan and (iv) other related matters. By the voting deadline of April 5, 2018 the Plan received approval from every single class of creditors and holders of interests entitled to vote, exceeding the required thresholds for acceptance of the Plan. The confirmation hearing for the Plan is currently scheduled for April 17, 2018. If the Plan is confirmed by the Bankruptcy Court, once each of the conditions precedent to the Plan’s effectiveness have been satisfied or waived, the Plan will become effective and each of the Debtors will emerge from the Chapter 11 proceedings. The Plan provides for, among other things, that: • Seadrill Limited will be dissolved under the laws of Bermuda following the confirmation of the Plan; • the Debtors will enter into amended senior credit facilities with its senior credit facility lenders; • holders of general unsecured claims will receive 15% of the common stock of Seadrill Limited’s successor, “New Seadrill” (such shares, “New Seadrill Common Shares”) (prior to dilution by the Primary Structuring Fee and the Employee Incentive Plan as defined below under “-Issuance and Distribution of the New Securities under the Plan and the Investment Agreement”); • the Debtors will conduct the rights offerings described below under “-Rights Offering,” with certain non-eligible holders of general unsecured claims entitled to participate pro rata in a $23 million cash recovery pool; • an additional $17 million in cash will be distributed to holders of general unsecured claims, other than claims held by the Commitment Parties as of September 12, 2017 or January 5, 2018, as applicable; • an additional $17 million in cash, less fees and expenses, will be distributed to the shipyards; and • if the general unsecured claims vote in favor of the Plan, holders of Seadrill’s existing equity will receive 2% of the New Seadrill Common Shares (prior to dilution by the Primary Structuring Fee and the Employee Incentive Plan defined below under “-Issuance and Distribution of the New Securities under the Plan and the Investment Agreement”). Rights Offerings Pursuant to the Plan and an order of the Bankruptcy Court approving the rights offering procedures, eligible holders in certain classes of general unsecured claims against the Debtors will be offered the right to participate in (i) a rights offering (the “Notes Rights Offering”) of up to $119.4 million in aggregate principal amount of new secured notes (“New Secured Notes”) to be issued by a subsidiary of New Seadrill (“NSNCo”) and a corresponding pro rata portion of 57.5% of New Seadrill Common Shares issued to holders who participate in the Notes Rights Offering and (ii) a rights offering of up to $48.1 million in value of New Seadrill Common Shares (the “Equity Rights Offering”). The New Secured Notes and the New Seadrill Common Shares to be acquired by the Commitment Parties under the Investment Agreement will be reduced to the extent the rights are exercised in each of the Notes Rights Offering and the Equity Rights Offering. The Commitment Parties will not participate in either the Notes Rights Offering or the Equity Rights Offering in accordance with the terms of the Investment Agreement. Issuance and Distribution of the New Securities under the Plan and the Investment Agreement Subject to the terms and conditions of the Plan and the amended Investment Agreement, on the Effective Date, (i) NSNCo will issue approximately $880 million in principal amount of New Secured Notes; and (ii) New Seadrill expects to issue: • up to 25% of the New Seadrill Common Shares (prior to dilution by the Primary Structuring Fee and the Employee Incentive Plan), plus any excess New Seadrill Common Shares, in exchange for $200 million paid in cash by the Commitment Parties to the Investment Agreement, which amount paid by the Commitment Parties will be reduced by an amount up to $48.1 million paid by participants in the Equity Rights Offering; • up to 57.5% of the New Seadrill Common Shares (prior to dilution by the Primary Structuring Fee and the Employee Incentive Plan) to the purchasers of the New Secured Notes, which will include the Commitment Parties and the participants in the Notes Rights Offering, on a pro rata basis in accordance with the amount of New Secured Notes issued to such purchasers; • (i) 5% of the New Seadrill Common Shares (prior to dilution by the Employee Incentive Plan) to Hemen on account of a primary structuring fee (the “Primary Structuring Fee”) and (ii) 0.5% of the New Seadrill Common Shares to certain other Commitment Parties (prior to dilution by the Primary Structuring Fee and the Employee Incentive Plan) on a pro rata basis in accordance with each such Commitment Party’s respective equity commitment percentage. Subject to the conditions of the Investment Agreement, the Commitment Parties agreed to purchase the full principal amount of the New Secured Notes and the associated 57.5% of the New Seadrill Common Shares (prior to dilution by the Primary Structuring Fee and the Employee Incentive Plan) for $880 million in cash, less the principal amount purchased by participants in the Notes Rights Offering. On the Effective Date, an employee incentive plan will be implemented by New Seadrill (the “Employee Incentive Plan”) which will (a) reserve an aggregate of 10% of the New Seadrill Common Shares, on a fully diluted, fully distributed basis, for grants made from time to time to employees of New Seadrill; and (b) otherwise contain terms and conditions (including with respect to participants, allocation, structure, and timing of issuance) generally consistent with those prevailing in the market at the discretion of the board of directors of New Seadrill. Liabilities subject to compromise Liabilities subject to compromise distinguish pre-petition liabilities which may be affected by the Chapter 11 proceedings from those that are not (such as fully secured liabilities that are not expected to be compromised) and those post-petition. These amounts represent our allowed claims and our best estimate of claims expected to be allowed which will be resolved as part of the bankruptcy proceedings. Liabilities subject to compromise represent our estimate of known or potential pre-petition claims to be resolved in connection with the Chapter 11 proceedings. Such claims remain subject to future adjustments which may result from: (i) negotiations; (ii) actions of the Bankruptcy Court; (iii) disputed claims; (iv) rejection of executory contracts and unexpired leases; (v) the determination as to the value of any collateral securing claims; (vi) proofs of claim; or (vii) other events. Such future adjustments will potentially be material. Liabilities subject to compromise include the following: (In US$ millions) December 31, 2017 Senior undersecured or impaired external debt 5,371 Unsecured bonds 2,334 Derivatives previously recorded at fair value 249 Loss on Newbuilding global settlement agreement 1,064 Accounts payable and other liabilities 103 Accrued interest payable 50 Amount due to related party 20 Liabilities subject to compromise 9,191 While operating as a Debtor-in-Possession under Chapter 11 of the Bankruptcy Code, the Debtor may sell, otherwise dispose of, or liquidate assets, or settle liabilities, subject to the approval of the Bankruptcy Court or otherwise as permitted in the ordinary course of business, in amounts other than those reflected in the Consolidated Financial Statements. Moreover, a plan of reorganization could materially change the amounts and classifications of assets and liabilities in the historical Consolidated Financial Statements. Interest expense During bankruptcy proceedings we continue to make interest payments on the secured credit facilities. These are treated as adequate protection payments which are recognized as a reduction in the principal balance of secured credit facilities held within "Liabilities subject to compromise" in the Consolidated Balance Sheets. $81 million of adequate protection payments have been recognized from Petition date to December 31, 2017 . The Debtors have discontinued recording interest on unsecured bond facilities classified as liabilities subject to compromise from the Petition Date. Contractual interest on liabilities subject to compromise not reflected in the Consolidated Statement of Operations was $129 million . Potential claims The Debtors have filed with the Bankruptcy Court schedules and statements setting forth, among other things, the assets and liabilities of the Debtors, subject to the assumptions filed in connection therewith. The schedules and statements may be subject to further amendment or modification after filing. All holders of pre-petition claims except governmental units were required to file proofs of claim by January 3, 2018 (the ‘‘Bar Date’’). Governmental units holding claims against the Debtors are required to file proof of claim by March 12, 2018. As of April 5, 2018, 1,575 claims totaling approximately $19.2 billion had been filed with the Bankruptcy Court against the Debtors. It is possible that claimants will file amended claims in the future, including claims amended to assign values to claims originally filed with no designated value. Through the claims resolution process, we have identified, and we expect to continue to identify, claims that we believe should be disallowed by the Bankruptcy Court because they are duplicative, have been later amended or superseded, are without merit, are overstated or for other reasons. We will file objections with the Bankruptcy Court as necessary for claims we believe should be disallowed. Claims we believe are allowable are reflected in ‘‘Liabilities Subject to Compromise’’ in the Consolidated Balance Sheets. Through the claims resolution process, differences in amounts scheduled by the Debtors and claims filed by creditors will be investigated and resolved, including through the filing of objections with the Bankruptcy Court where appropriate. In light of the number of claims filed, the claims resolution process will take additional time to complete, and it may continue after our emergence from bankruptcy. Accordingly, the ultimate number and amount of allowed claims is not presently known, nor can the ultimate recovery with respect to allowed claims be presently ascertained. Executory Contracts Under the Bankruptcy Code, the Debtors have the right to assume, amend and assume, or reject certain contracts, subject to the approval of the Bankruptcy Court and certain other conditions. Generally, the assumption of a contract requires a debtor to satisfy pre-petition obligations under the contract, which may include payment of pre-petition liabilities in whole or in part. Rejection of a contract is typically treated as a breach occurring as of the moment immediately preceding the Chapter 11 filing. Subject to certain exceptions, this rejection relieves the debtor from performing its future obligations under the contract but entitles the counterparty to assert a pre-petition general unsecured claim for damages. Parties to contracts rejected by a debtor may file proofs of claim against that debtor’s estate for damages. As part of the Chapter 11 proceedings, the Debtors negotiated and announced a global settlement with various creditors, including Samsung Heavy Industries Co., Ltd. ("Samsung") and Daewoo Shipbuilding & Marine Engineering Co., Ltd ("DSME"). The amendments to the RSA and Investment Agreement provided for, among other items, an agreement regarding the allowed claim of the newbuild shipyards Samsung and DSME, and an immediate cessation of all litigation and discovery efforts in relation to the plan of reorganization as well as the Debtors’ rejection and recognized termination of the newbuild contracts. The settlement agreement is contingent on confirmation of the Plan. Following the allowed claim agreement in respect of the Samsung and DSME, we have recognized a liability of $1.064 billion at December 31, 2017, and due to the Plan anticipating the rejection and termination of the newbuild contracts we have recognized an impairment of the newbuild assets related to the West Dorado, West Draco, West Aquila and the West Libra, totaling $696 million , in the year ended December 31, 2017. Reorganization items, net Incremental costs incurred directly as a result of the Bankruptcy Filing and gains on the settlement of liabilities under the Plan are classified as “Reorganization items, net” in the Consolidated Statements of Operations. The following table summarizes reorganization items: (In US$ millions) December 31, 2017 Advisory and professional fees (66 ) New investor commitment fees (53 ) Unamortized debt issuance costs (66 ) Gain or loss on pre-petition allowable claims (3 ) Loss on Newbuilding global settlement agreement (1,064 ) Interest income on surplus cash invested 4 Reversal of issuing entities credit risk on derivatives (89 ) Reorganization items, net (1,337 ) For the year ended December 31, 2017, Seadrill paid approximately $72 million for reorganization items, net in cash. This includes $53 million of new investor commitment fees, which are included as 'Debt fee paid' in our Consolidated Statement of Cash Flows. Condensed Combined Debtors Financial Statements When one or more entities in the consolidated group are in bankruptcy and one or more entities in the consolidated group are not in bankruptcy, the reporting entity is required to disclose the condensed combined financial statements of only the entities in bankruptcy. The financial statements below represent the Condensed Combined Financial Statements of the entities that filed for bankruptcy (“debtor in possession” or “DIP”). Intercompany transactions between the Debtors have been eliminated in the financial statements herein. Debtors' Condensed Combined Balance Sheet (in US$ millions) as at December 31, 2017 2017 ASSETS Cash and cash equivalents 1,157 Restricted cash 81 Marketable securities 124 Accounts receivables, net 291 Amount due from related parties - current 213 Intra group receivables 1,064 Other current assets 257 Total current assets 3,187 Non-current assets Investment in associated companies 1,346 Drilling units 12,568 Shares in subsidiaries 6,501 Deferred tax assets 10 Equipment 29 Amount due from related parties - non-current 547 Intra group non-current assets 475 Other non-current assets 81 Total non-current assets 21,557 Total assets 24,744 LIABILITIES AND EQUITY Current liabilities Trade accounts payable 69 Amounts due to related parties - current 6 Intra group liabilities 961 Other current liabilities 240 Total current liabilities 1,276 Liabilities subject to compromise 9,191 Non-current liabilities Deferred tax liabilities 108 Intra group non-current liabilities 1,434 Other non-current liabilities 69 Total non-current liabilities 1,611 Total equity 12,666 Total liabilities and equity 24,744 Debtors' Condensed Combined Statement of Operations (in US$ millions) for the period of September 12, 2017 to December 31, 2017 2017 Operating revenues Contract revenues 463 Reimbursable revenues 12 Intra group revenues 27 Other revenues 1 Total operating revenues 503 Loss on disposals (95 ) Contingent consideration realized 9 Operating expenses Vessel and rig operating expenses (262 ) Reimbursable expenses (11 ) Depreciation and amortization (229 ) Intra group expenses (16 ) Loss on impairment of long lived assets (696 ) Total operating expenses (1,214 ) Operating loss (797 ) Financial items and other income/(expense), net Interest income/(expense), net 21 Share in results from associated companies (net of tax) 67 Loss on impairment of investments (841 ) Loss on derivative financial instruments (2 ) Foreign exchange gain 8 Reorganization Items, net (1,337 ) Other financial items and other income, net 8 Total financial items and other expense, net (2,076 ) Loss before income taxes (2,873 ) Income tax expense (67 ) Net loss (2,940 ) Net loss attributable to the non-controlling interest (67 ) Net loss attributable to the parent (2,873 ) Debtors' Condensed Combined Statement of Cash Flows (in US$ millions) for the period of September 12, 2017 to December 31, 2017 2017 Cash Flows from Operating Activities Net cash provided by operating activities 294 Cash Flows from Investing Activities Additions to newbuildings (1 ) Additions to drilling units and equipment (20 ) Contingent consideration received 28 Change in restricted cash (10 ) Proceed from repayment of short term loan to related parties 8 Net cash provided by investing activities 5 Cash Flows from Financing Activities Repayments of debt (77 ) Debt fees paid (53 ) Net cash used in financing activities (130 ) Effect of exchange rate changes on cash and cash equivalents (2 ) Net increase in cash and cash equivalents 167 Cash and cash equivalents at beginning of the year 990 Cash and cash equivalents at the end of year 1,157

Segment information

Segment information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment information	Segment information Operating segments We provide drilling and related services to the offshore oil and gas industry. We have been organized into three operating segments: 1. Floaters : Services encompassing drilling, completion and maintenance of offshore exploration and production wells. The drilling contracts relate to semi-submersible rigs and drillships for harsh and benign environments in mid-, deep- and ultra-deep waters; 2. Jack-up rigs : Services encompassing drilling, completion and maintenance of offshore exploration and production wells. The drilling contracts relate to jack-up rigs for operations in harsh and benign environments; and 3. Other : Operations including management services to third parties and related parties. Income and expenses from these management services are classified under this segment. Segment results are evaluated on the basis of operating income, and the information given below is based on information used for internal management reporting. Revenues Year ended December 31, (In US$ millions) 2017 2016 2015 Floaters 1,387 2,212 2,906 Jack-up rigs 617 865 1,293 Other 84 92 136 Total 2,088 3,169 4,335 Depreciation and amortization Year ended December 31, (In US$ millions) 2017 2016 2015 Floaters 601 600 570 Jack-up rigs 197 210 208 Other — — 1 Total 798 810 779 Operating income – net income Year ended December 31, (In US$ millions) 2017 2016 2015 Floaters (622 ) 759 340 Jack-up Rigs (112 ) 267 664 Other 6 — 15 Operating income (728 ) 1,026 1,019 Unallocated items: Total financial items and other (2,308 ) (982 ) (1,446 ) (Loss)/income before income taxes (3,036 ) 44 (427 ) Drilling Units and Newbuildings - Total assets (In US$ millions) December 31, 2017 December 31, 2016 Floaters 9,956 11,751 Jack-up Rigs 3,508 4,056 Total Drilling Units and Newbuildings 13,464 15,807 Assets held for sale 126 128 Investments in Associated companies 1,473 2,168 Marketable securities 124 110 Cash and restricted cash 1,359 1,443 Other assets 1,436 2,010 Total 17,982 21,666 Capital expenditures – fixed assets Year ended December 31, (In US$ millions) 2017 2016 2015 Floaters 128 192 950 Jack-up Rigs 22 35 95 Total 150 227 1,045 Geographic segment data Revenues are attributed to geographical segments based on the country of operations for drilling activities, i.e. the country where the revenues are generated. The following presents our revenues and fixed assets by geographic area: Revenues Year ended December 31, (In US$ millions) 2017 2016 2015 Angola 482 419 527 Brazil 358 491 877 United States 291 370 371 Norway 219 475 641 Nigeria 193 431 499 Others (1) 545 983 1,420 Total Revenue 2,088 3,169 4,335 (1) Other countries represent countries in which we operate that individually had revenues representing less than 10% of total revenues earned for any of the periods presented. Major customers In the years ended December 31, 2017 , 2016 and 2015 , we had the following customers with contract revenues greater than 10% in any of the years presented: Year ended December 31, 2017 2016 2015 Total S.A Group ("Total") 25 % 18 % 16 % Petroleo Brasileiro S.A ("Petrobras") 19 % 17 % 19 % LLOG 15 % 13 % 9 % Exxon Mobil Corp ("Exxon") 7 % 13 % 14 % Statoil ASA ("Statoil") 4 % 10 % 12 % Fixed assets – drilling units (1) (In US$ millions) December 31, 2017 December 31, 2016 Norway 2,258 2,456 Spain 2,016 944 Brazil 1,816 1,884 Malaysia 1,809 673 USA 1,266 1,298 Others (2) 4,051 5,598 Total 13,216 12,853 (1) The fixed assets referred to in the table above exclude assets under construction. Asset locations at the end of a period are not necessarily indicative of the geographic distribution of the revenues or operating profits generated by such assets during such period. (2) Other countries represent countries in which we operate that individually had fixed assets representing less than 10% of total fixed assets for any of the periods presented.

Other revenues

Other revenues	12 Months Ended
	Dec. 31, 2017
Revenues [Abstract]
Other revenues	Other revenues Other revenues consist of the following: Year ended December 31, (In US$ millions) 2017 2016 2015 Revenues related party 110 100 119 Amortization of unfavorable contracts 43 65 116 External management fees with third parties 1 19 30 Termination revenue 8 69 — Total 162 253 265 Related party revenue relate to management support and administrative services provided during the year to Seadrill's associates in which we maintain an investment. Refer to Note 30 "Related party transactions" for more information. The unfavorable contract values in 2017 , 2016 and 2015 arose primarily from our acquisition of Sevan Drilling ASA, refer to Note 20 "Goodwill and other intangible assets and liabilities" for more information. The residual unfavorable contract amortized in 2016 arose from the Sevan Driller, which finished amortizing in March 2016 on termination of contract. The residual unfavorable contract amortized in 2015 arose from our acquisition of the Songa Eclipse, which finished amortizing in May 2015. External management fees relate to the operational, administrative and support services that we provide to SapuraKencana as part of the agreement that Seadrill entered into when we sold majority of the tender rig business. As the associated rigs were not operational from April 2017 no further management fees were recognized after this date. Refer to Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information. The termination revenue in 2017 relates to the early termination fee recognized for contracts cancelled on the West Hercules for $8 million . The total termination fee for the West Hercules was $66 million , with $58 million of revenue recognized in 2016 and remaining $8 million recognized in January 2017. In 2016, an additional $11 million of termination revenue was recognized for the early termination on the West Epsilon contract.

Loss on disposals

Loss on disposals	12 Months Ended
	Dec. 31, 2017
Proceeds from Sale of Productive Assets [Abstract]
(Loss)/gain on disposals	Loss on disposals We have recognized the following (losses)/gains on disposals: (In US$ millions) Net proceeds/recoverable amount Book value on disposal (Loss)/gain Year ended December 31, 2017: Sale of West Triton 75 109 (34 ) Sale of West Mischief 75 146 (71 ) Sale of West Resolute 75 136 (61 ) Disposal of Sevan Developer contract — 75 (75 ) Sale of West Rigel 126 128 (2 ) Other — 2 (2 ) Total for year ended December 31, 2017 351 596 (245 ) Year ended December 31, 2016: Total for year ended December 31, 2016 — — — Year ended December 31, 2015: Cancellation of West Mira 199 279 (80 ) Sale of West Polaris 235 312 (77 ) SeaMex Limited 1,240 1,059 181 West Rigel transferred to Asset held for sale 128 210 (82 ) Other — 5 (5 ) Total for year ended December 31, 2015 1,802 1,865 (63 ) Loss on disposals in 2017 Sale of West Triton, West Mischief and West Resolute On April 29, 2017 we reached an agreement with Shelf Drilling to sell the West Triton, West Mischief and West Resolute for a total consideration of $225 million . The West Triton and West Resolute were delivered in May 2017, whilst the West Mischief was delivered in September 2017. The sale resulted in a loss on disposal of $166 million . Disposal of Sevan Developer contract In October 2014, Sevan entered an agreement with Cosco to defer the delivery date of the Sevan Developer for twelve months with four subsequent options to extend the date for further periods of six months, until October 2017. On October 30, 2015, April 15, 2016 and October 15, 2016 three of the options were enacted, with $26.3 million , or 5% of the contract price, plus associated costs, refunded to Sevan on each occasion. On April 27, 2017, the final delivery deferral agreement for the Sevan Developer was deferred to May 31, 2017 to finalize negotiations. As an agreement was not reached, the remaining installment of $26.3 million was refunded to Sevan, taking the delivery installment back to the $526.0 million contract price. In July 2017, Sevan and Cosco agreed to defer the Sevan Developer delivery period until June 30, 2020. The contract amendment included a contract termination clause for Cosco and therefore it was deemed that Sevan had lost control of the asset and therefore derecognized the newbuild asset, which was held at $620 million , construction obligation held at $526 million , and accrued interest and other liabilities held at $19 million , resulting in a net loss on disposal of $75 million . The Sevan Developer will remain in China at the Cosco Shipyard and we will continue marketing the rig for an acceptable drilling contract where financing can be obtained to allow delivery. West Rigel settlement agreement On April 5, 2018, we entered into a settlement and release agreement, subject to Bankruptcy Court approval, with Jurong in respect of the West Rigel whereby we agreed that the share of sale proceeds from the sale of the West Rigel by Jurong would be $126 million . We consider this agreement provides additional evidence of the value of the asset held for sale at December 31, 2017, and have therefore reflected the agreed share of sales proceeds in the value of the asset held for sale at the balance sheet date, recognizing a $2 million loss on disposal. (Gain) / Loss on disposals in 2016 No gains or losses were recognized in the year ended December 31, 2016 . (Gain) / Loss on disposals in 2015 Cancellation of the West Mira On September 14, 2015, we cancelled the construction contract for the West Mira with Hyundai Samho Heavy Industries Co Ltd. (“HSHI”), due to the Shipyard’s inability to deliver the unit within the timeframe required under the contract. The carrying value of the newbuild at the date of cancellation was $315 million , which included $170 million of pre-delivery installments paid to HSHI, with the remainder relating to purchased equipment, internally capitalized construction costs and capitalized interest. Under the contract terms, we have the right to recoup the $170 million in pre-delivery installments, plus accrued interest. On October 12, 2015, HSHI launched arbitration proceedings under the contract. In the year ended December 31, 2015 , we reclassified from "Newbuildings" a receivable of $170 million plus accrued interest of $29 million , which was presented in "Other non-current assets" on the Consolidated Balance Sheet as a receivable from the shipyard. The total receivable represented management's assessment at that time as the most probable outcome based on facts and circumstances, and advice from external counsel, who had been engaged for the arbitration process. The resulting net loss on disposal recognized was $80 million , which is included in “ Loss on disposals ” in the 2015 Consolidated Statement of Operations. On March 13, 2017, we reached settlement with HSHI and Seadrill received a cash payment of $170 million , representing the yard installment receivable excluding any additional accrued interest. This payment was received on the March 14, 2017. We recorded a non-cash impairment of $44 million for the year ended December 31, 2016 , to reflect the difference in the carrying value of the West Mira receivable and the cash payment to be received. The non-cash impairment comprises $31 million that has been taken against "Loss on impairment of long lived assets" and $13 million has been taken against "Interest income" in the 2016 Consolidated Statement of Operations. As at December 31, 2016 , the receivable presented in "Other current assets" on the Consolidated Balance Sheet was $170 million . We are redeploying equipment, totaling $48 million , within Seadrill’s remaining fleet, and have not written off these amounts. SeaMex Limited During the year ended December 31, 2014, we entered into a joint venture agreement with an investment fund controlled by Fintech Advisory Inc. (“Fintech”), for the purpose of owning and managing certain jack-up drilling units located in Mexico under contract with Pemex. The transaction was completed on March 10, 2015, when Fintech subscribed for a 50% ownership interest in the joint venture company, SeaMex Limited (“SeaMex”), which was previously 100% owned by us. As a result of the transaction we deconsolidated certain entities as at March 10, 2015, and recognized our remaining 50% investment in the joint venture at fair value. Refer to Note 11 "Disposal of businesses and deconsolidation of subsidiaries" for more information. West Rigel Transferred to Asset held for sale On December 2, 2015 , the West Rigel was classified as an asset held for sale. As at the transfer date the West Rigel was held at its book value of $210 million and a loss on disposal of 82 million was recognized. As at December 31, 2017 , $126 million is still held for sale. Refer to Note 35 "Assets held for sale" and Note 37 "Subsequent Events" for more information . Sale of West Polaris On June 19, 2015, we sold the entities that owned and operated the West Polaris to Seadrill Operating LP, a consolidated subsidiary of Seadrill Partners LLC and 42% owned by us. Refer to Note 11 "Disposal of businesses and deconsolidation of subsidiaries" for more information . Contingent Consideration Following the sale of the West Polaris to Seadrill Operating LP in 2015 and the sale of the West Vela to Seadrill Capricorn Holdings LLC in 2014, we have recognized the following contingent considerations: Year Ended December 31, (In US$ millions) 2017 2016 2015 West Polaris earn out realized 13 8 32 West Vela earn out realized 14 13 15 Total contingent consideration recognized 27 21 47

Interest expense

Interest expense	12 Months Ended
	Dec. 31, 2017
Interest Expense [Abstract]
Interest expense	Interest expense Year ended December 31, (In US$ millions) 2017 2016 2015 Gross interest expense 313 451 475 Capitalized interest (28 ) (39 ) (60 ) Interest expense 285 412 415 During bankruptcy proceedings we continue to make interest payments on secured credit facilities classified as liabilities subject to compromise. These are treated as adequate protection payments which are recognized as a reduction in the principal balance of secured credit facilities held within "Liabilities subject to compromise" in the Consolidated Balance Sheets. $81 million of adequate protection payments have been recognized from Petition date to December 31, 2017 . The Debtors have discontinued recording interest on unsecured bond facilities classified as liabilities subject to compromise from the Petition Date. Non-Debtors continue to pay interest under the normal contractual terms, which continue to be recognized in the Statement of Operations. During Chapter 11 no interest on newbuildings has been capitalized as interest payments made during bankruptcy proceedings are treated as adequate protection payments.

Impairment loss on marketable s

Impairment loss on marketable securities and investments in associated companies	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Impairment loss on marketable securities and investments in associated companies (restated)	Impairment loss on marketable securities and investments in associated companies The table below summarizes the total impairments of investments during the years ending December 31, 2017 , 2016 and 2015 : Year ended December 31, (In US$ millions) 2017 2016 2015 Impairments of Marketable securities (refer to Note 13) Seadrill Partners - Common Units — 153 574 SapuraKencana — — 178 Total impairment of marketable securities investments (reclassification from OCI) — 153 752 Impairments of Investment in associated companies and joint ventures (refer to Note 16) Seadrill Partners - Total direct ownership investments 723 400 302 Seadrill Partners - Subordinated units 82 180 125 Seadrill Partners - Seadrill member interest and IDRs — 73 106 SeaMex Limited 36 76 — Itaunas Drilling, Camburi Drilling, and Sahy Drilling — 13 — Total impairment of investments in associated companies and joint ventures 841 742 533 Total impairment of investments 841 895 1,285 Impairment loss recognized for the year ended December 31, 2017 Seadrill Partners - Subordinated units and direct ownership interests - Impairment of Equity Method Investment Whilst the investments in Seadrill Partners held under the equity method are not publicly traded, the value of the publicly traded units remained lower than the carrying value ascribed to the equity method investments using managements assumptions for a sustained period. We have determined this to be representative of an other than temporary impairment. As at December 31, 2017, the carrying value of the subordinated units was found to exceed the fair value by $82 million , and the carrying value of the direct ownership interests was found to exceed the fair value by $723 million . We have recognized this impairment of the investments within “Loss on impairment of investments” in the Consolidated Statement of Operations. The fair value of these investments were derived using an income approach, which discounts future free cash flows (“DCF model”). The estimated future free cash flows associated with the investments are primarily based on expectations around applicable day rates, drilling unit utilization, operating costs, capital and long-term maintenance expenditures, applicable tax rates and industry conditions. The cash flows were estimated over the remaining useful economic lives of the underlying assets but no longer than 30 years in total, and discounted using an estimated market participant weighted average cost of capital of 9.75% . The DCF model derived an enterprise value of the investments, after which associated debt was subtracted to provide equity values. The implied valuation of Seadrill Partners derived from the DCF model was crosschecked against the market price of Seadrill Partners’ common units. Due to the significant influence we have on Seadrill Partners, there is in implied significant influence premium, which represents the additional value we would place over and above the market price of Seadrill Partners in order to maintain this significant influence. This is similar in thought to an implied control premium. We have evaluated the difference by reviewing the implied control premium as compared to other market transactions within the industry. We deem the implied control premium to be reasonable in the context of the data considered. The assumptions used in the DCF model were derived from significant unobservable inputs (representative of Level 3 inputs for Fair Value Measurement) and are based on management’s judgments and assumptions available at the time of performing the impairment test. We employ significant judgment in developing these estimates and assumptions including the following: • forecast dayrates for our drilling contracts; • utilization rates; • operating costs and overheads; • estimated annual capital expenditure, cost of rig replacement and/or enhancement programs; • estimated maintenance, inspections or other costs associated with a rig after completion/termination of the contract; • remaining useful life of each rig; and • estimated tax rates. The underlying assumptions and assigned probabilities of occurrence for utilization and dayrate scenarios were developed using a methodology that examines historical data for each rig, which considers the rig’s age, rated water depth and other attributes and then assesses its future marketability in light of the current and projected market environment at the time of assessment. Other assumptions, such as operating, maintenance and inspection costs, are estimated using historical data adjusted for known developments and future events that are anticipated by management at the time of the assessment. Management’s assumptions are necessarily subjective and are an inherent part of our asset impairment evaluation, and the use of different assumptions could produce results that differ from those reported. Management’s assumptions involve uncertainties about future demand for our services, dayrates, expenses and other future events, and management’s expectations may not be indicative of future outcomes. Significant unanticipated changes to these assumptions could materially alter our analysis in testing an asset for potential impairment. SeaMex Limited - Impairment of investment in Joint Venture The deteriorating market conditions in the oil and gas industry and supply and demand conditions in the offshore drilling sector in which SeaMex operates is considered to be an indicator of impairment. We have determined the length and severity of the deterioration of market conditions to be representative of an other than temporary impairment. As such we have measured and recognized an other than temporary impairment of the investment in SeaMex as at December 31, 2017. The fair value was derived using an income approach, which discounts future free cash flows (“DCF model”). The estimated future free cash flows associated with the investment were primarily based on expectations around applicable day rates, drilling unit utilization, operating costs, capital and long-term maintenance expenditures and applicable tax rates. The cash flows were estimated over the remaining useful economic lives of the underlying assets but no longer than 30 years in total, and discounted using an estimated market participant weighted average cost of capital of 10.25% . The DCF model derived an enterprise value of the investments, after which associated debt was subtracted to provide equity values. The carrying value of the investment was found to exceed the fair value by $36 million . We have recognized this impairment of the investments within “Loss on impairment of investments” in the Consolidated Statement of Operations. The assumptions used in the DCF model were derived from unobservable inputs (level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. The use of different assumptions, particularly with regard to the most sensitive assumptions concerning estimated future dayrates and utilization and the assumed market participant discount rate, would have a material impact on the impairment charge recognized and our Consolidated Statement of Operations. In addition, if actual events differ from management’s estimates, or to the extent that these estimates are adjusted in the future, our financial condition and results of operations could be affected in the period of any such change of estimate. Impairment loss recognized for the year ended December 31, 2016 Seadrill Partners - Common Units - Impairment of marketable securities During the period between September 30, 2015 and September 30, 2016 , Seadrill Partners’ unit price fell by approximately 62% , on both a spot price and trailing three-month average basis. Management determined that the investment in Seadrill Partners’ common units was other than temporarily impaired due to the length and severity of the reduction in value below historic cost. As a result we have impaired the investment, recognizing an impairment charge of $153 million within "Loss on impairment of investments". This impairment charge includes a reclassification of losses previously recognized within Other Comprehensive Income. During the three months ended December 31, 2016, Seadrill Partners’ unit price increased from approximately $3.53 at September 30, 2016 to $4.20 at December 31, 2016 . As at December 31, 2016, an unrealized gain of $17 million had been recognized in “accumulated other comprehensive income,” as a result of remeasuring the value of our investment in the common units of Seadrill Partners to the market price as at December 31, 2016. Seadrill Partners - Subordinated units and direct ownership interests - Impairment of Equity Method Investment As at September 30, 2016 , the carrying value of the subordinated units was found to exceed the fair value by $180 million , and the carrying value of the direct ownership interests was found to exceed the fair value by $400 million . We recognized this impairment of the investments within “Loss on impairment of Investments” in the Consolidated Statement of Operations. In the period from September 30, 2016 to December 31, 2016 no additional impairment was recognized due to the increase in the value of the traded units. The assumptions used in the DCF model were derived from unobservable inputs (classified as level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. Seadrill Partners - Member interest - Impairment of Cost method investments As at September 30, 2016, the reduction in value of the Seadrill Partners common units was determined to be an indicator of impairment of the Seadrill member interest. The fair value was determined using the Monte Carlo model, updated for applicable assumptions as at September 30, 2016. The carrying value of the investment was found to exceed the fair value by $73 million . We recognized this impairment within “Loss on impairment of Investments” in the Consolidated Statement of Operations. The assumptions used in the Monte Carlo model were derived from both observable and unobservable inputs (classified as level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. SeaMex Limited - Impairment of investment in Joint Venture During the year ended December 31, 2014 we entered into a joint venture agreement with an investment fund controlled by Fintech, for the purpose of owning and managing certain jack-up drilling units located in Mexico under contract with Pemex. The West Oberon , West Intrepid , West Defender , West Courageous and West Titania jack-up drilling rigs were included within the joint venture. The transaction was completed on March 10, 2015, when Fintech subscribed for a 50% ownership interest in SeaMex, which was previously 100% owned by us, and the jack-up drilling rigs were acquired by SeaMex from Seadrill. As a result of the transaction we no longer control the entities that own and operate these jack-up drilling rigs, and accordingly we deconsolidated these entities as at March 10, 2015, and recognized our retained 50% investment in the joint venture at fair value. The deteriorating market conditions in the oil and gas industry and supply and demand conditions in the offshore drilling sector in which SeaMex operates is considered to be an indicator of impairment. We have determined the length and severity of the deterioration of market conditions to be representative of an other than temporary impairment. As such we measured and recognized an other than temporary impairment of the investment in SeaMex as at September 30, 2016. The fair value was derived using an income approach, which discounts future free cash flows (“DCF model”). The estimated future free cash flows associated with the investment were primarily based on expectations around applicable day rates, drilling unit utilization, operating costs, capital and long-term maintenance expenditures and applicable tax rates. The cash flows were estimated over the remaining useful economic lives of the underlying assets but no longer than 30 years in total, and discounted using an estimated market participant weighted average cost of capital of 11% . The DCF model derived an enterprise value of the investments, after which associated debt was subtracted to provide equity values. The carrying value of the investment was found to exceed the fair value by $76 million . We recognized this impairment of the investments within “Loss on impairment of Investments” in the Consolidated Statement of Operations. Itaunas Drilling, Camburi Drilling, and Sahy Drilling - Impairment of investment in Joint Venture Itaunas Drilling BV, Camburi Drilling BV and Sahy Drilling BV are joint ventures which each have a contract to construct one drillship. The joint ventures are owned 70% by Sete International (a subsidiary of Sete Brasil Participacoes SA) and 30% by us. During the year ended December 31, 2016, due to the deteriorating market conditions in the offshore drilling industry, the uncertainty around the financial condition of Sete Brasil Participacoes SA, and the uncertainty around the recoverability of the investments, we recognized an other than temporary impairment of $13 million to write down the value of these investments to nil. We recognized this impairment within “Loss on impairment of investments” in the Consolidated Statement of Operations. Impairment loss recognized for the year ended December 31, 2015 Seadrill Partners - Common Units - Impairment of marketable securities At September 30, 2015 management determined that the investment in Seadrill Partners’ common units was other than temporarily impaired due to the length and severity of the reduction in value below historic cost. As a result we impaired the investment, recognizing an impairment charge of $574 million within “Loss on impairment of investments.” This impairment charge represents a reclassification of losses previously recognized within Other Comprehensive Income. The amount reclassified out of "Accumulated other comprehensive income" into earnings was determined on the basis of average cost. Seadrill Partners - Subordinated units and direct ownership interests - Impairment of Equity Method Investment As at September 30, 2015, the carrying value of the subordinated units was found to exceed the fair value by $125 million , and the carrying value of the direct ownership interests was found to exceed the fair value by $302 million . We recognized this impairment of the investments within “Loss on impairment of Investments” in the Consolidated Statement of Operations. The assumptions used in the DCF model were derived from unobservable inputs (classified as level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. Seadrill Partners - Member interest - Impairment of Cost method investments The reduction in value of the Seadrill Partners Common Units was determined to be an indicator of impairment of the Seadrill member interest. The fair value was determined using the Monte Carlo model, updated for applicable assumptions as at September 30, 2015. The carrying value of the investment was found to exceed the fair value by $106 million . We recognized this impairment within “Loss on impairment of investments” in the Consolidated Statement of Operations. The assumptions used in the Monte Carlo model were derived from both observable and unobservable inputs (classified as level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. SapuraKencana - Impairment of marketable securities During the period since September 30, 2014, to September 30, 2015, SapuraKencana’s share price fell by approximately 45% as a result of deteriorating market conditions in the oil and gas industry. Between June 30, 2015 and September 30, 2015, the value of the investment fell by approximately 20% , as a result of the declining share price and USD:MYR exchange rate. At September 30, 2015, management determined that the investment in SapuraKencana was other than temporarily impaired due to the length and severity of the reduction in value below historic cost. As a result we impaired the investment, recognizing an impairment charge of $167 million within “Loss on impairment of investments”. This impairment charge represents a reclassification of losses previously recognized within Other Comprehensive Income. The amount reclassified out of "Accumulated other comprehensive income" into earnings was determined on the basis of average cost. During the period to December 31, 2015 we recognized an additional net impairment charge to bring the carrying value of the asset to the realizable value of $195 million . The resulting net impairment was a loss of $ 11 million , which was recognized within "Loss on impairments of investments" in the Consolidated Statement of Operations. As a result, the total impairment charge recognized for the period to December 31, 2015 was $178 million . On April 27, 2016 , we sold our entire shareholding in SapuraKencana for net proceeds of $ 195 million , net of transaction costs. Investment in associated companies We have the following investments that are or have been recorded using the equity method for the periods presented in these Consolidated Financial Statements: Ownership percentage December 31, 2017 December 31, 2016 December 31, 2015 Archer Limited ("Archer") Note 1 39.7 % 39.9 % Seabras Sapura Participacoes Ltda ("Seabras Sapura Participacoes") 50.0 % 50.0 % 50.0 % Seabras Sapura Holding GmbH ("Seabras Sapura Holding") 50.0 % 50.0 % 50.0 % Itaunas Drilling B.V. ("Itaunas Drilling") 30.0 % 30.0 % 30.0 % Camburi Drilling B.V. ("Camburi Drilling") 30.0 % 30.0 % 30.0 % Sahy Drilling B.V. ("Sahy Drilling") 30.0 % 30.0 % 30.0 % Seadrill Partners ("SDLP") Note 2 Note 2 Note 2 SeaMex Ltd. ("SeaMex") 50.0 % 50.0 % 50.0 % (1) As part of their financial restructuring, Archer completed two share issuances in March and April 2017, which diluted Seadrill's ownership interest to 15.7% as at December 31, 2017 . In April 2017, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized it as an available-for-sale security. (2) As at the deconsolidation date of Seadrill Partners on January 2, 2014, we recognized our ownership interests in Seadrill Partners and direct ownership interests in Seadrill Partners subsidiaries, at fair value at the date of deconsolidation. Refer to the Seadrill Partners paragraph below for additional information. At year-end the book values of our investment in associated companies are as follows: (In US$ millions) December 31, 2017 December 31, 2016 Archer (1) N/A — Seabras Sapura Participacoes 63 47 Seabras Sapura Holding 290 227 Itaunas Drilling — — Camburi Drilling — — Sahy Drilling — — Seadrill Partners - Total direct ownership interests 857 1,537 Seadrill Partners - Subordinated units 97 157 Seadrill Partners - Seadrill member interest and IDRs (2) 64 64 Seamex Ltd. 102 136 Total 1,473 2,168 (1) In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized it as an available-for-sale security. (2) The Seadrill Partners - Seadrill member interest and Incentive Distribution Rights (“IDR’s”) are accounted for as cost-method investments on the basis that they do not represent common stock interests and their fair value is not readily determinable. The investments are held at cost and not subsequently re-measured. For more details on the deconsolidation of Seadrill Partners see Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information. Quoted market prices for all of our other equity investments are not available because, other than Seadrill Partners Common Units, these companies are not publicly traded. Seadrill Partners subordinated units are not tradable and hence have no quoted market price. Archer Archer is a company listed on the Oslo Stock Exchange and provides drilling and well services. Prior to February 2011, Archer was a consolidated subsidiary. In February 2011, we deconsolidated Archer and as a result accounted for our interest as an investment in an associated company. On February 8, 2013, Seadrill were allocated 82,003,000 shares in the private placement of Archer, amounting to a value of $98 million . In addition, as consideration for acting as an underwriter to the placement, we received another 2,811,793 shares, amounting to a value of $3 million . The consideration for the shares was settled against the existing $55 million loan to Archer, with the remainder of the consideration funded by a $43 million loan from Archer, which was repaid on February 27, 2013. As part of their financial restructuring, Archer completed two share issuances in March and April 2017, which diluted Seadrill's ownership interest in Archer to 15.7% as at December 31, 2017 . The restructuring also resulted in financial guarantees provided by Seadrill being settled in April and June 2017 and related party loan arrangements with Seadrill being significantly reduced. In April 2017, we concluded that we no longer had significant influence over Archer's financial and operating decisions, primarily as a result of the reduction in our shareholding and the significant reduction in our interests in related debt and guarantees. Our investment in Archer was therefore derecognized as an investment in associate and recognized as an available-for-sale security at the closing carrying value of the equity investment in associate, nil . A $10 million accumulated other comprehensive income gain related to the equity method investment was recycled to the Consolidated Statement of Operations. For transactions and balances with Archer, refer to Note 30 "Related party transactions" for more information. Seabras Sapura Participacoes and Seabras Sapura Holding Seabras Sapura Participacoes S.A. is a company incorporated in Brazil, which is currently constructing one pipe-laying vessel. It is 50% owned by TL Offshore Sdn. Bhd., a subsidiary of SapuraKencana, and 50% owned by Seadrill. Seabras Sapura Holding GmbH is a company incorporated in Austria, which is owns five pipe-laying vessels. It is 50% owned by TL Offshore Sdn. Bhd. and 50% owned by Seadrill. For transactions and balances with Seabras Sapura Participacoes and Seabras Sapura Holding, please refer to Note 30 "Related party transactions". Itaunas Drilling, Camburi Drilling, and Sahy Drilling Itaunas Drilling BV is a company incorporated in Holland, which has contracted to construct a drillship. It is 70% owned by Sete International GmbH, (a subsidiary of Sete Brasil Participacoes SA), and 30% owned by Seadrill. Camburi Drilling BV is a company incorporated in Holland, which has contracted to construct a drillship. It is 70% owned by Sete International GmbH and 30% owned by Seadrill. Sahy Drilling BV is a company incorporated in Holland, which has contracted to construct a drillship. It is 70% owned by Sete International GmbH and 30% owned by the Seadrill. During the twelve months ended December 31, 2016, due to the deteriorating market conditions in the offshore drilling industry, the uncertainty around the financial condition of Sete Brasil Participacoes SA, and the uncertainty around the recoverability of the investments, we recognized an other than temporary impairment of $13 million to write down the value of these investments to nil. We have recognized this impairment within “Loss on impairment of investments” in the Consolidated Statement of Operations. Refer to Note 8 "Impairment loss on marketable securities and investments in associated companies" for more information. Seadrill Partners Seadrill’s investment in Seadrill Partners accounted for under the equity method is comprised of the following: (a) Subordinated units - our holdings of subordinated units of Seadrill Partners are accounted for under the equity method on the basis that the subordinated units are considered to be ‘in-substance common stock’. The subordination period will end on the satisfaction of various tests as prescribed in the Operating Agreement of Seadrill Partners. Upon the expiration of the subordination period, the subordinated units will convert into Common Units. (b) Direct Ownership interests - Seadrill holds ownership interests in the following entities controlled by Seadrill Partners as at December 31, 2017 : i. 42% in Seadrill Operating LP : Seadrill Operating LP is a limited partnership and is controlled by its General Partner, Seadrill Operating GP LLC, which is wholly owned by Seadrill Partners. ii. 49% Seadrill Capricorn Holdings LLC : Seadrill Capricorn Holdings LLC is a limited liability company. There is only one class of member interest which is deemed to represent voting common stock. iii. 39% in Seadrill Deepwater Drillship Ltd and 49% indirect interest in Seadrill Mobile Units (Nigeria) Ltd. : Both entities are limited companies and only have one class of stock, which is deemed to represent voting common stock. All of our direct ownership interests are accounted for under the equity method as we are deemed to have significant influence over these entities through its voting rights and by virtue of Seadrill’s representation on the Board of Seadrill Partners. Purchase of 10% interest in Seadrill Mobile Units Nigeria Limited On December 5, 2016 , our wholly owned subsidiary Seadrill UK Ltd. acquired a 10% interest that an unrelated party, HH Global Alliance Investments Limited (“HHL”) held in Seadrill Mobile Units (Nigeria) Ltd, the service company for West Capella , for a notional value of $6.6 million . Following the completion of this transaction Seadrill UK Ltd. owns 49% of Seadrill Mobile Units Nigeria Limited, with the remaining 51% being owned by subsidiaries of Seadrill Partners. Simultaneously HHL acquired from Seadrill UK Ltd. a 49% interest in Seadrill Nigeria Operations Limited, the service company for West Jupiter for a notional value of $6.6 million . The impact of these transactions was to increase Seadrill’s direct ownership interest in Seadrill Partners by $6.6 million , and to recognize HHL’s non-controlling interest in Seadrill Nigeria Operations Ltd of $6.6 million . Impairment During the years ending December 31, 2017 , 2016 and 2015 , we recognized other than temporary impairments on the equity method investments in Seadrill Partners for $805 million , $653 million and $533 million respectively. Refer to Note 8 "Impairment loss on marketable securities and investments in associated companies" for more information. For transactions and balances with Seadrill Partners, please refer to Note 30 "Related party transactions". SeaMex During the year ended December 31, 2014, we entered into a joint venture agreement with an investment fund controlled by Fintech, for the purpose of owning and managing certain jack-up drilling units located in Mexico under contract with Pemex. The transaction was completed on March 10, 2015, when Fintech subscribed for a 50% ownership interest in the joint venture company, SeaMex, which was previously 50% owned by us, and SeaMex simultaneously purchased the jack-up drilling rigs from Seadrill Limited. As a result of the transaction we no longer control the entities that own and operate these jack-up drilling units, and accordingly we have deconsolidated these entities as at March 10, 2015, and has recognized our remaining 50% investment in the joint venture at fair value. The fair value of the retained 50% equity interest in the SeaMex joint venture was determined by reference to the price paid by Fintech to obtain a 50% equity interest in the Disposal group from Seadrill. We accounts for our 50% investment in the joint venture under the equity method. Refer to Note 11 "Disposals of business and deconsolidation of subsidiaries" for further information. During the year ended December 31, 2015 both the JV partners each made an additional $19 million of equity investment in SeaMex while retaining their 50% share in the JV. Impairment During the years ended December 31, 2017 and December 31, 2016 , we recognized other than temporary impairments on the equity method investments in SeaMex Limited for $36 million and $76 million respectively. Refer to Note 8 "Impairment loss on marketable securities and investments in associated companies" for further information. For transactions and balances with SeaMex, refer to Note 30 "Related party transactions". Summary financial information of the equity method investees Summarized Consolidated Balance Sheet information of our equity method investees is as follows: Balance at December 31, 2017 (In US$ millions) Current assets Non-current assets Current liabilities Non-current liabilities Non-Controlling interest Archer N/A N/A N/A N/A N/A Seabras Sapura Participacoes 126 299 131 169 — Seabras Sapura Holding 341 1,331 542 845 — Seadrill Partners 1,214 5,317 546 3,284 1,398 SeaMex 294 1,036 222 666 — Total 1,975 7,983 1,441 4,964 1,398 Balance at December 31, 2016 (In US$ millions) Current assets Non-current assets Current liabilities Non-current liabilities Non-Controlling interest Archer 287 773 313 718 — Seabras Sapura Participacoes 100 317 149 174 — Seabras Sapura Holding 258 1,393 509 988 — Seadrill Partners 1,214 5,567 665 3,580 1,343 SeaMex 296 1,095 145 818 — Total 2,155 9,145 1,781 6,278 1,343 Summarized Consolidated Statement of Operations information for our equity method investees is as follows: Year ended December 31, 2017 (In US$ millions) Operating revenues Net operating income Net income Net income attributable to non-controlling interest Archer N/A N/A N/A — Seabras Sapura Participacoes 76 60 34 — Seabras Sapura Holding 186 184 126 — Seadrill Partners 1,128 464 235 94 SeaMex 239 80 15 — Total 1,629 788 410 94 Year ended December 31, 2016 (In US$ millions) Operating revenues Net operating (loss)/income Net (loss)/income Net income attributable to non-controlling interest Archer 818 (41 ) (166 ) — Seabras Sapura Participacoes 148 46 39 — Seabras Sapura Holding 241 155 89 — Seadrill Partners 1,600 818 546 265 SeaMex 280 119 36 — Total 3,087 1,097 544 265 Year ended December 31, 2015 (In US$ millions) Operating revenues Net operating (loss)/income Net (loss)/income Net income attributable to non-controlling interest Archer 1,321 (13 ) (359 ) — Seabras Sapura Participacoes 53 3 1 — Seabras Sapura Holding 124 76 51 — Seadrill Partners 1,742 844 488 231 Seamex 238 79 24 — Total 3,478 989 205 231 At the year end the share of recorded equity in the statutory accounts of our associated companies were as follows: (In US$ millions) December 31, 2017 December 31, 2016 December 31, 2015 Archer (1) N/A 15 79 Seabras Sapura Participacoes 63 47 24 Seabras Sapura Holding 143 77 19 Seadrill Partners (2) N/A N/A N/A Seamex 221 218 200 Total 427 357 322 (1) In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized as an available-for-sale security. (2) We account for our direct interests in operating subsidiaries of Seadrill Partners, and our ownership of Seadrill Partners Subordinated Units, under the equity method. Our share of Seadrill Partners recorded equity consists of the equity attributable to non-controlling interests in Seadrill Partners, and additionally a proportionate share of equity attributable to Seadrill Partners’ unitholders. The equity attributable to non-controlling interest in Seadrill Partners as at December 31, 2017 was $1,398 million (December 31, 2016: $1,343 million ). Seadrill’s holding in the subordinated units represents 18.0% of the limited partner interests in Seadrill Partners. Total equity attributable to Seadrill Partners' unitholders as at December 31, 2017 was $1,304 million (December 31, 2016: $1,193 million ).

Taxation

Taxation	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Taxation	Taxation Income taxes consist of the following: Year ended December 31, (In US$ millions) 2017 2016 2015 Current tax expense: Bermuda — — — Foreign 56 151 177 Deferred tax expense: Bermuda — — — Foreign 10 48 31 Total tax expense 66 199 208 Effective tax rate (2.2 )% 452.3 % (48.7 )% The effective tax rate for the year ended December 31, 2017 is (2.2)% as compared to a rate for 2016 of 452.3% . The rate reflects no tax relief on the majority of the $1,337 million of the Reorganization items, net, the $841 million loss on impairment of investments, the $696 million loss on impairment of Newbuildings or the $11 million gain on derivative financial instruments, as well as no tax chargeable or deductible on the $245 million disposal losses. This is due to these items largely falling within the zero tax rate Bermuda companies. This is in comparison to 2016 where no tax relief on the $895 million loss on impairment of investments or $74 million loss on derivative financial instruments. We are headquartered in Bermuda, where a tax exemption has been granted until 2035. Other jurisdictions in which we and our subsidiaries operate are taxable based on rig operations. A loss in one jurisdiction may not be offset against taxable income in another jurisdiction. Thus, we may pay tax within some jurisdictions even though it might have losses in others. The income taxes for the years ended December 31, 2017 , 2016 and 2015 differed from the amount computed by applying the Bermudan statutory income tax rate of 0% as follows: Year ended December 31. (In US$ millions) 2017 2016 2015 Income taxes at statutory rate — — — Effect of change on uncertain tax positions relating to prior year (5 ) 28 — Effect of unremitted earnings of subsidiaries 3 (4 ) 38 Effect of taxable income in various countries 68 175 170 Total tax expense 66 199 208 During the year ended December 31, 2015, we reviewed our assertion of indefinite reinvestment of unremitted earnings of subsidiaries and determined that we no longer consider such earnings to be indefinitely reinvested. We have recognized a deferred tax liability balance of $37 million in 2017 ( $34 million in 2016). Deferred income taxes Deferred income taxes reflect the impact of temporary differences between the amount of assets and liabilities recognized for financial reporting purposes and such amounts recognized for tax purposes. The net deferred tax assets/(liabilities) consist of the following: Deferred tax assets: (In US$ millions) December 31, December 31, Pensions and stock options 4 3 Provisions 49 28 Net operating losses carried forward 255 272 Other — 2 Gross deferred tax assets 308 305 Valuation allowance (230 ) (245 ) Deferred tax assets, net of valuation allowance 78 60 Deferred tax liabilities: (In US$ millions) December 31, December 31, Property, plant and equipment 138 126 Unremitted Earnings of Subsidiaries 37 34 Gross deferred tax liabilities 175 160 Net deferred tax (liability)/asset (97 ) (100 ) As at December 31, 2017 , deferred tax assets related to net operating loss (“NOL”) carry forwards was $255 million ( 2016 : $272 million ), which can be used to offset future taxable income. NOL carry forwards which were generated in various jurisdictions, include $248 million ( 2016 : $237 million ) that will not expire and $7 million ( 2016 : $35 million ) that will expire between 2018 and 2037 if unutilized. A valuation allowance of $216 million as at December 31, 2017 ( 2016 : $238 million ) on the NOL carry forwards has been recorded where we do not expect to generate future taxable income. Uncertain tax positions As at December 31, 2017 , we had uncertain tax positions of $55 million and interest and penalties of $12 million , of which $3 million was included in other current liabilities and $45 million was included in other non-current liabilities, and $19 million was presented as a reduction of deferred tax assets. The changes to our uncertain tax positions were as follows: Year ended December 31, (In US$ millions) 2017 2016 2015 Balance at the beginning of the period 44 9 9 Increases as a result of positions taken in prior periods 23 35 — Increases as a result of positions taken during the current period — 2 — Decreases as a result of positions taken in prior periods (9 ) (2 ) — Decreases as a result of positions taken in the current period — — — Decreases due to settlements (3 ) — — Balance at the end of the period 55 44 9 Accrued interest and penalties totaled $12 million and $2 million as of December 31, 2017 and December 31, 2016 respectively and were included in other liabilities on our consolidated Balance Sheet. We recognized expenses of $10 million during the year ended December 31, 2017 ( $2 million expenses recognized in the year ended December 31, 2016 and nil in the year ended December 31, 2015 ), related to interest and penalties for unrecognized tax benefits on the income tax expense line in the accompanying Consolidated Statement of Operations. As at December 31, 2017 , if recognized, $48 million of our unrecognized tax benefits, including interest and penalties, would have a favorable impact on our effective tax rate. Tax returns and open years We are subject to taxation in various jurisdictions. Tax authorities in certain jurisdictions examine our tax returns and some have issued assessments. We are defending our tax positions in those jurisdictions. The Brazilian tax authorities have issued a series of assessments with respect to our returns for certain years up to 2012 for an aggregate amount equivalent to $161 million including interest and penalties. We are robustly contesting these assessments including filing relevant appeals. An adverse outcome on these proposed assessments could result in a material adverse impact on our consolidated statement of financial position, results of operations or cash flows. The Nigerian tax authorities have issued a series of claims and assessments both directly and lodged through the Chapter 11 process with respect to returns for subsidiaries for certain years up to 2016 for an aggregate amount equivalent to c. $171 million . We are robustly contesting these assessments including filing relevant appeals in Nigeria and it is also intended that one or more formal objections against these claims for distribution purposes will be filed in the US court. An adverse outcome on these proposed assessments could result in a material adverse impact on our consolidated statement of financial position, results of operations or cash flows. The following table summarizes the earliest tax years that remain subject to examination by other major taxable jurisdictions in which we operate. Jurisdiction Earliest Open Year Angola 2015 Nigeria 2014 United States 2014 Norway 2013 Brazil 2008

Loss per share

Loss per share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Loss per share	Loss per share The computation of basic (loss)/earnings per share (“EPS”) is based on the weighted average number of shares outstanding during the period. Diluted EPS includes the effect of the assumed conversion of potentially dilutive instruments. The components of the numerator for the calculation of basic and diluted EPS are as follows: (In US$ millions) 2017 2016 2015 Net loss attributable to the parent (2,973 ) (181 ) (634 ) Less: Allocation to participating securities — — — Net loss available to stockholders (2,973 ) (181 ) (634 ) Effect of dilution — — — Diluted net loss available to stockholders (2,973 ) (181 ) (634 ) The components of the denominator for the calculation of basic and diluted EPS are as follows: (In US$ millions) 2017 2016 2015 Basic earnings per share: Weighted average number of common shares outstanding 505 501 493 Diluted earnings per share: Effect of dilutive convertible bonds — — — Effect of dilutive share options (1) — — — Weighted average number of common shares outstanding adjusted for the effects of dilution 505 501 493 (1) Certain stock options have been excluded from the calculation of diluted EPS because their exercise price exceeded our average share price during the calculation period. (In US$) 2017 2016 2015 Basic loss per share (5.89 ) (0.36 ) (1.29 ) Diluted loss per share (5.89 ) (0.36 ) (1.29 ) Interests in the existing Seadrill common shares will be extinguished under the plan of reorganization contemplated by the RSA. Instead the plan will provide holders of Seadrill Common stock with 2% of new Seadrill equity, subject to dilution by the primary structuring fee and an employee incentive plan, provided that general unsecured creditors vote to accept the plan. If Seadrill general unsecured creditors do not accept the plan, holders of existing Seadrill common shares will receive no recovery. The RSA contemplates certain releases and exculpations and implementation of a customary equity-based employee incentive plan at closing. The transactions contemplated by the RSA are subject to court approval and other terms and conditions.

Disposals of businesses and dec

Disposals of businesses and deconsolidation of subsidiaries	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Disposals of businesses and deconsolidation of subsidiaries	Disposals of businesses and deconsolidation of subsidiaries Disposals in 2017 There were no disposals of businesses and deconsolidation of subsidiaries in the year ended December 31, 2017 . Disposals in 2016 There were no disposals of businesses and deconsolidation of subsidiaries in the year ended December 31, 2016. Disposals in 2015 Disposal of the West Polaris On June 19, 2015 , we sold the entities that owned and operated the West Polaris (the “Polaris business”), to Seadrill Operating LP (“Seadrill Operating”), a consolidated subsidiary of Seadrill Partners LLC and 42% owned by us. The entities continue to be related parties subsequent to the sale. The purchase price consisted of an initial enterprise value of $540 million , less debt assumed of $336 million . The fair value of consideration recognized on disposal was $235 million , which comprised of $204 million of cash consideration, and a working capital adjustment of $31 million , due to the net working capital of the Polaris business being greater than the required working capital prescribed in the sale and purchase agreement. Additional contingent consideration in the form of a seller’s credit of $50 million is also potentially due from Seadrill Partners in 2021, which will carry interest at a rate of 6.5% per annum. The repayment of the seller’s credit is contingent on the future re-contracted day rate. During the 3 -year period following the completion of the current customer contract, the final amount payable will be adjusted downwards to the extent the average re-contracted operating day rate (net of commissions), adjusted for utilization, over the period, is less than $450 thousand per day. If the rig is off contract during this period, the reduction is equal to $450 thousand per day. In addition, we may be entitled to receive further contingent consideration from Seadrill Partners, consisting of (a) any day rates earned by Seadrill Partners in excess of $450 thousand per day, adjusted for daily utilization, tax and agency commission for the remainder of the ExxonMobil contract completing in February 2018 and (b) 50% of any day rate earned above $450 thousand per day, adjusted for daily utilization, tax and agency commission fee after the conclusion of the existing contract until 2025. In February 2016, the drilling contract with ExxonMobil was amended such that the day rate for the West Polaris was reduced from $653 thousand per day to $490 thousand per day, effective January 1, 2016. Our accounting policy is not to recognize contingent consideration before it is considered realizable and has therefore not recognized on disposal any amounts receivable relating to the elements of consideration which are contingent on future events. From the disposal date of the West Polaris on June 19, 2015 to December 31, 2015 , we have recognized $32 million in contingent consideration, as it became realized, within “Contingent consideration realized” included within "Operating income". In the years ended December 31, 2016 and December 31, 2017 , we recognized an additional $8 million and $13 million in contingent consideration respectively. The loss recognized at the time of disposal of the Polaris business was $77 million , after taking into account a goodwill allocation of $41 million . Refer to Note 6 "(Loss)/gain on disposals" for more information. As at June 19, 2015 Initial enterprise value 540 Less: Debt assumed (336 ) Initial purchase price 204 Plus: Working capital adjustment 31 Adjusted initial purchase price 235 Cash 204 Plus: Working capital receivable 31 Fair value of purchase consideration recognized on disposal 235 Less: net carrying value of assets and liabilities (271 ) Less: allocated goodwill to subsidiaries (41 ) Loss on disposal (77 ) Under the terms of various agreements between Seadrill and Seadrill Partners LLC, which were entered into in connection with the initial public offering of Seadrill Partners LLC, Seadrill will continue to provide management, technical and administrative services to the Polaris business. Refer to Note 30 "Related party transactions" for more information of these services and agreements. The sale of the Polaris business does not qualify for reporting as a discontinued operation as the sale of the Polaris business is not considered to represent a strategic shift that is expected to have a major effect on our operations and financial results. SeaMex Limited During the year ended December 31, 2014, we entered into a Joint Venture agreement ("JV agreement") with an investment fund controlled by Fintech Advisory Inc. (“Fintech”), for the purpose of owning and managing certain jack-up drilling units located in Mexico under contract with Pemex. The West Oberon , West Intrepid , West Defender , West Courageous and West Titania jack-up drilling rigs (“the jack-up drilling rigs”) were included within the joint venture. The transaction was completed on March 10, 2015 , when Fintech subscribed for a 50% ownership interest in the joint venture company, SeaMex Limited (“SeaMex” or the "JV"), which was previously 100% owned by us, and SeaMex simultaneously purchased the jack-up drilling rigs from Seadrill Limited. As a result of the transaction, we no longer control the entities that own and operate these jack-up drilling units (the “Disposal Group”), and accordingly we have deconsolidated these entities as at March 10, 2015, and recognized our remaining 50% investment in the joint venture at fair value. The fair value of the retained 50% equity interest in the SeaMex joint venture was determined by reference to the price paid by Fintech to obtain a 50% equity interest in the disposal group from Seadrill. We account for our 50% investment in the joint venture under the Equity Method. Total consideration in respect of the Disposal Group was $1,077 million from SeaMex to Seadrill. This was comprised of net cash of $586 million , a seller’s credit receivable of $250 million , short term related party receivable balances of $91 million and a direct settlement of Seadrill’s debt facilities relating to the West Oberon amounting to $150 million . Subsequently, $162 million of the related party balance was received when the West Titania was refinanced. The seller’s credit bears interest at a rate of LIBOR plus a margin of 6.50% and matures in December 2019. Refer to Note 30 "Related party transactions" for more information. Seadrill utilized the cash consideration to repay outstanding debt facilities in respect of the West Courageous , West Defender , West Intrepid and West Titania . Refer to Note 22 "Long-term debt" for more information. The total recognized gain on disposal was $181 million , after taking into account a goodwill allocation of $49 million , which has been presented in our Consolidated Statement of Operations, under “ Loss on disposals ” included within "Operating income" attributable to the jack-up segment. We have not presented this Disposal Group as a discontinued operation in the Consolidated Statement of Operations as it does not represent a strategic shift that has (or will have) a major effect on our operations and financial results. (In US$ millions) As at March 10, 2015 Fair value of consideration received Net cash consideration received 749 Seller’s credit recognized 250 Direct repayment of debt by the JV on behalf of Seadrill 150 Consideration receivable in respect of West Titania 162 Other related party balances payable (71 ) Cash paid to acquire 50% interest in the JV (163 ) Fair value of consideration received 1,077 Fair value of retained 50% investment in Seamex Limited 163 Carrying value of net assets Current assets Cash and cash equivalents 40 Deferred tax assets - short term 8 Other current assets 20 Total current assets 68 Non-current assets Drilling units 969 Deferred tax asset - long term 4 Other non-current assets 86 Goodwill 49 Total non-current assets 1,108 Total assets 1,176 Liabilities Current liabilities Trade accounts payable (1 ) Other current liabilities (56 ) Total current liabilities (57 ) Non-current liabilities Other non-current liabilities (60 ) Total non-current liabilities (60 ) Total liabilities (117 ) Carrying value of net assets 1,059 Gain on disposal 181 In connection with the JV agreement, SeaMex entered into a management support agreement with Seadrill Management, a wholly owned subsidiary of ours, pursuant to which Seadrill Management provides SeaMex with certain management and administrative services. The services provided by Seadrill Management are charged at cost plus management fee of 8% of Seadrill’s costs and expenses incurred in connection with providing these services. The agreement can be terminated by SeaMex by providing 120 days written notice. Accounting for basis differences Our investments in Seadrill Partners that are accounted for under the equity method (subordinated units and direct ownership interests) were initially recognized at fair value upon deconsolidation. Basis differences therefore exist between the fair value of the investments and the underlying carrying values of the investees’ net assets at the date of deconsolidation. A valuation exercise has been performed for each separate investment accounted for under the equity method, in order to allocate these basis differences to identifiable assets and liabilities, with any residual amount recognized as goodwill. Differences have been allocated to depreciable or amortizable assets or liabilities and will be amortized over the estimated useful economic life of the underlying assets and liabilities. This amortization is recognized in the Consolidated Statement of Operations in the "Share in results from associated companies" line. The basis difference has been accounted for as follows: (i) The basis difference assigned to drilling units is being depreciated over the remaining estimated useful lives of the units; (ii) The basis difference relating to the drilling contracts is being amortized over the remaining term of the contract; and (iii) The Company will not amortize the difference assigned to goodwill, but will consider any indicators of impairment. Following other than temporary impairments recognized in September 2015 , September 2016 and December 31, 2017 the basis difference for drilling units, contracts and goodwill caused Seadrill's share of basis difference to fall by $427 million , $567 million and $246 million . The remaining basis difference for drilling units and goodwill the period ended December 31, 2017 was $1 million and $6 million respectively.

Restricted cash

Restricted cash	12 Months Ended
	Dec. 31, 2017
Restricted Cash and Investments [Abstract]
Restricted cash	Restricted cash Restricted cash includes: (In US$ millions) December 31, 2017 December 31, 2016 Danske guarantee agreement 70 70 Cash pledged as collateral 6 — Tax withholding deposits 5 5 Other 23 — Short-term restricted cash 104 75 Long-term restricted cash — — Total restricted cash 104 75

Marketable securities

Marketable securities	12 Months Ended
	Dec. 31, 2017
Marketable Securities [Abstract]
Marketable securities	Marketable securities The historic cost of marketable securities is marked to market, with changes in fair value recognized in the Consolidated Statement of Other Comprehensive Income. Marketable securities held by us are equity securities considered to be available-for-sale. The following tables summarize the carrying values of the marketable securities in the Consolidated Balance Sheet: As at December 31, 2017 (In US$ millions) Amortized Cumulative unrealized fair value gains Carrying Archer — 28 28 Seadrill Partners - Common Units 93 3 96 Total 93 31 124 As at December 31, 2016 (In US$ millions) Amortized Cumulative unrealized fair value gains Carrying Seadrill Partners - Common Units 93 17 110 Total 93 17 110 The following table summarizes the gross realized gains and losses from marketable securities during the years presented: Year ended December 31, 2017 (In US$ millions) Gross realized gains Gross realized losses Gross unrealized gains Gross unrealized losses Gross proceeds from sales Recognition and purchases Gain/(loss) reclassified into income Archer — — 42 (14 ) — — — Seadrill Partners - Common Units — — 8 (22 ) — — — Total — — 50 (36 ) — — — Year ended December 31, 2016 (In US$ millions) Gross realized gains Gross realized losses Gross unrealized gains Gross unrealized losses Gross proceeds from sales Recognition and purchases Loss reclassified into income Sapura Kencana — — — — 195 — — Seadrill Partners - Common Units — — 69 (52 ) — — (153 ) Total — — 69 (52 ) 195 — (153 ) Year ended December 31, 2015 (In US$ millions) Gross realized gains Gross realized losses Gross unrealized gains Gross unrealized losses Gross proceeds from sales Recognition and purchases Loss reclassified into income Sapura Kencana — — — (130 ) — — (178 ) Seadrill Partners - Common Units — — 16 (346 ) — — (574 ) Total — — 16 (476 ) — — (752 ) SapuraKencana During the year ended December 31, 2015 we recognized an other than temporary impairment charge of $167 million on the investment in SapuraKencana, which was recorded within “Loss on impairment of investments.” This impairment charge represents a reclassification of losses previously recognized within Other Comprehensive Income. Refer to Note 8 "Impairment loss on marketable securities and investments in associated companies" for more information. An additional net impairment charge was recognized to bring the carrying value of the asset to the realizable value of $195 million as at December 31, 2015 . The resulting net impairment was a loss of $11 million , which is recognized within "Loss on impairments of investments" in the Consolidated Statement of Operations. The total investment impairment charge for SapuraKencana recognized in the year ended December 31, 2015 was $178 million . On April 27, 2016 , we sold our entire shareholding in SapuraKencana for net proceeds of $195 million , net of transaction costs. Seadrill Partners Common Units Our holding of the voting common units of Seadrill Partners are accounted for as marketable securities on the basis that during the subordination period the common units have preferential dividend and liquidation rights, and therefore do not represent a ‘in-substance common stock’ interest as defined by U.S. GAAP. These securities were recognized on January 2, 2014 at the quoted market price and are re-measured at fair value each reporting period. At September 30, 2015 management determined that the investment in Seadrill Partners’ Common Units was other than temporarily impaired, recognizing an impairment charge of $574 million within “Loss on impairment of investments”. At September 30, 2016 , management further determined the investment to be other than temporarily impaired due to the continuing length and severity of the reduction in value below historic cost. As a result we have further impaired the investment, recognizing an additional impairment charge of $153 million within "Loss on impairment of investments". This impairment charge includes a reclassification of current period and historical fair value losses previously recognized within Other Comprehensive Income. The amount reclassified out of "Accumulated other comprehensive income" into earnings was determined on the basis of average cost. No other than temporary impairment was recognized during the year ended December 31, 2017 as the fair value of the common units was greater than book value at December 31, 2017. Marketable securities in Seadrill Partners, with a fair value of $96 million , are in an unrealized gain position as at December 31, 2017 . The total cumulative unrealized holding gains as at December 31, 2017 amounted to $3 million ( December 31, 2016 : total accumulated gains of $17 million ). Archer As part of their financial restructuring, Archer completed two share issuances in March and April 2017, which diluted Seadrill's ownership interest in Archer to 15.7% as at December 31, 2017 . As part of the restructuring the financial guarantee's and a significant portion of the performance guarantees provided by Seadrill were settled and the related party loan arrangements with Seadrill significantly reduced. In April 2017, as a result of these activities, we concluded that we no longer had significant influence over Archer's financial and operating decisions, primarily as a result of the reduction in our shareholding and the significant reduction in our interests in related debt and guarantees. Our investment in Archer was therefore derecognized as an investment in associate and recognized as an available-for-sale security at the closing carrying value of the equity investment in associate, being nil . A $10 million accumulated other comprehensive income gain related to the equity method investment was recycled to the statement of operations and presented within other financial items. A $28 million gain was subsequently recognized in other comprehensive income as at December 31, 2017 , reflecting the value of the marketable security at the closing Archer share price of NOK 10.05 .

Accounts receivable

Accounts receivable	12 Months Ended
	Dec. 31, 2017
Accounts Receivable, Net, Current [Abstract]
Accounts receivable	Accounts receivable Accounts receivable are presented net of allowances for doubtful accounts. The allowance for doubtful accounts receivables at December 31, 2017 was $35 million ( 2016 : $31 million ; 2015 : $39 million ). We did not recognize any bad debt expense in 2017 , 2016 , or 2015 , but have instead reduced contract revenue for the disputed amounts.

Other current assets

Other current assets	12 Months Ended
	Dec. 31, 2017
Other Assets [Abstract]
Other current assets	Other current assets Other current assets include: (In US$ millions) December 31, 2017 December 31, 2016 Prepaid expenses 87 21 Deferred consideration (1) 80 135 Taxes receivable 24 25 Reimbursable amounts due from customers 15 21 Deferred mobilization cost 15 35 Receivable from ship-yard (2) — 170 Other current assets 36 88 Total other current assets 257 495 (1) On April 30, 2013, we completed the disposal of the tender rig business to SapuraKencana. The total consideration consisted of a non-contingent deferred consideration of $145 million , bearing interest at LIBOR plus 5% , which was due in April 2016 . During the year ended December 31, 2016, SapuraKencana repaid $10 million of the principal and paid $25 million of interest. On August 28, 2017 this was converted into a formalized loan agreement whereby $5 million is repaid each month, with the residual due to be repaid on August 3, 2018. We expect the entire amount will be recoverable. (2) The receivable from shipyard relates to the West Mira , which reached settlement for $170 million on March 13, 2017. For details on the arbitration process and subsequent settlement, refer to Note 6 " Loss on disposals " for more information.

Investment in associated compan

Investment in associated companies	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Investment in associated companies	Impairment loss on marketable securities and investments in associated companies The table below summarizes the total impairments of investments during the years ending December 31, 2017 , 2016 and 2015 : Year ended December 31, (In US$ millions) 2017 2016 2015 Impairments of Marketable securities (refer to Note 13) Seadrill Partners - Common Units — 153 574 SapuraKencana — — 178 Total impairment of marketable securities investments (reclassification from OCI) — 153 752 Impairments of Investment in associated companies and joint ventures (refer to Note 16) Seadrill Partners - Total direct ownership investments 723 400 302 Seadrill Partners - Subordinated units 82 180 125 Seadrill Partners - Seadrill member interest and IDRs — 73 106 SeaMex Limited 36 76 — Itaunas Drilling, Camburi Drilling, and Sahy Drilling — 13 — Total impairment of investments in associated companies and joint ventures 841 742 533 Total impairment of investments 841 895 1,285 Impairment loss recognized for the year ended December 31, 2017 Seadrill Partners - Subordinated units and direct ownership interests - Impairment of Equity Method Investment Whilst the investments in Seadrill Partners held under the equity method are not publicly traded, the value of the publicly traded units remained lower than the carrying value ascribed to the equity method investments using managements assumptions for a sustained period. We have determined this to be representative of an other than temporary impairment. As at December 31, 2017, the carrying value of the subordinated units was found to exceed the fair value by $82 million , and the carrying value of the direct ownership interests was found to exceed the fair value by $723 million . We have recognized this impairment of the investments within “Loss on impairment of investments” in the Consolidated Statement of Operations. The fair value of these investments were derived using an income approach, which discounts future free cash flows (“DCF model”). The estimated future free cash flows associated with the investments are primarily based on expectations around applicable day rates, drilling unit utilization, operating costs, capital and long-term maintenance expenditures, applicable tax rates and industry conditions. The cash flows were estimated over the remaining useful economic lives of the underlying assets but no longer than 30 years in total, and discounted using an estimated market participant weighted average cost of capital of 9.75% . The DCF model derived an enterprise value of the investments, after which associated debt was subtracted to provide equity values. The implied valuation of Seadrill Partners derived from the DCF model was crosschecked against the market price of Seadrill Partners’ common units. Due to the significant influence we have on Seadrill Partners, there is in implied significant influence premium, which represents the additional value we would place over and above the market price of Seadrill Partners in order to maintain this significant influence. This is similar in thought to an implied control premium. We have evaluated the difference by reviewing the implied control premium as compared to other market transactions within the industry. We deem the implied control premium to be reasonable in the context of the data considered. The assumptions used in the DCF model were derived from significant unobservable inputs (representative of Level 3 inputs for Fair Value Measurement) and are based on management’s judgments and assumptions available at the time of performing the impairment test. We employ significant judgment in developing these estimates and assumptions including the following: • forecast dayrates for our drilling contracts; • utilization rates; • operating costs and overheads; • estimated annual capital expenditure, cost of rig replacement and/or enhancement programs; • estimated maintenance, inspections or other costs associated with a rig after completion/termination of the contract; • remaining useful life of each rig; and • estimated tax rates. The underlying assumptions and assigned probabilities of occurrence for utilization and dayrate scenarios were developed using a methodology that examines historical data for each rig, which considers the rig’s age, rated water depth and other attributes and then assesses its future marketability in light of the current and projected market environment at the time of assessment. Other assumptions, such as operating, maintenance and inspection costs, are estimated using historical data adjusted for known developments and future events that are anticipated by management at the time of the assessment. Management’s assumptions are necessarily subjective and are an inherent part of our asset impairment evaluation, and the use of different assumptions could produce results that differ from those reported. Management’s assumptions involve uncertainties about future demand for our services, dayrates, expenses and other future events, and management’s expectations may not be indicative of future outcomes. Significant unanticipated changes to these assumptions could materially alter our analysis in testing an asset for potential impairment. SeaMex Limited - Impairment of investment in Joint Venture The deteriorating market conditions in the oil and gas industry and supply and demand conditions in the offshore drilling sector in which SeaMex operates is considered to be an indicator of impairment. We have determined the length and severity of the deterioration of market conditions to be representative of an other than temporary impairment. As such we have measured and recognized an other than temporary impairment of the investment in SeaMex as at December 31, 2017. The fair value was derived using an income approach, which discounts future free cash flows (“DCF model”). The estimated future free cash flows associated with the investment were primarily based on expectations around applicable day rates, drilling unit utilization, operating costs, capital and long-term maintenance expenditures and applicable tax rates. The cash flows were estimated over the remaining useful economic lives of the underlying assets but no longer than 30 years in total, and discounted using an estimated market participant weighted average cost of capital of 10.25% . The DCF model derived an enterprise value of the investments, after which associated debt was subtracted to provide equity values. The carrying value of the investment was found to exceed the fair value by $36 million . We have recognized this impairment of the investments within “Loss on impairment of investments” in the Consolidated Statement of Operations. The assumptions used in the DCF model were derived from unobservable inputs (level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. The use of different assumptions, particularly with regard to the most sensitive assumptions concerning estimated future dayrates and utilization and the assumed market participant discount rate, would have a material impact on the impairment charge recognized and our Consolidated Statement of Operations. In addition, if actual events differ from management’s estimates, or to the extent that these estimates are adjusted in the future, our financial condition and results of operations could be affected in the period of any such change of estimate. Impairment loss recognized for the year ended December 31, 2016 Seadrill Partners - Common Units - Impairment of marketable securities During the period between September 30, 2015 and September 30, 2016 , Seadrill Partners’ unit price fell by approximately 62% , on both a spot price and trailing three-month average basis. Management determined that the investment in Seadrill Partners’ common units was other than temporarily impaired due to the length and severity of the reduction in value below historic cost. As a result we have impaired the investment, recognizing an impairment charge of $153 million within "Loss on impairment of investments". This impairment charge includes a reclassification of losses previously recognized within Other Comprehensive Income. During the three months ended December 31, 2016, Seadrill Partners’ unit price increased from approximately $3.53 at September 30, 2016 to $4.20 at December 31, 2016 . As at December 31, 2016, an unrealized gain of $17 million had been recognized in “accumulated other comprehensive income,” as a result of remeasuring the value of our investment in the common units of Seadrill Partners to the market price as at December 31, 2016. Seadrill Partners - Subordinated units and direct ownership interests - Impairment of Equity Method Investment As at September 30, 2016 , the carrying value of the subordinated units was found to exceed the fair value by $180 million , and the carrying value of the direct ownership interests was found to exceed the fair value by $400 million . We recognized this impairment of the investments within “Loss on impairment of Investments” in the Consolidated Statement of Operations. In the period from September 30, 2016 to December 31, 2016 no additional impairment was recognized due to the increase in the value of the traded units. The assumptions used in the DCF model were derived from unobservable inputs (classified as level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. Seadrill Partners - Member interest - Impairment of Cost method investments As at September 30, 2016, the reduction in value of the Seadrill Partners common units was determined to be an indicator of impairment of the Seadrill member interest. The fair value was determined using the Monte Carlo model, updated for applicable assumptions as at September 30, 2016. The carrying value of the investment was found to exceed the fair value by $73 million . We recognized this impairment within “Loss on impairment of Investments” in the Consolidated Statement of Operations. The assumptions used in the Monte Carlo model were derived from both observable and unobservable inputs (classified as level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. SeaMex Limited - Impairment of investment in Joint Venture During the year ended December 31, 2014 we entered into a joint venture agreement with an investment fund controlled by Fintech, for the purpose of owning and managing certain jack-up drilling units located in Mexico under contract with Pemex. The West Oberon , West Intrepid , West Defender , West Courageous and West Titania jack-up drilling rigs were included within the joint venture. The transaction was completed on March 10, 2015, when Fintech subscribed for a 50% ownership interest in SeaMex, which was previously 100% owned by us, and the jack-up drilling rigs were acquired by SeaMex from Seadrill. As a result of the transaction we no longer control the entities that own and operate these jack-up drilling rigs, and accordingly we deconsolidated these entities as at March 10, 2015, and recognized our retained 50% investment in the joint venture at fair value. The deteriorating market conditions in the oil and gas industry and supply and demand conditions in the offshore drilling sector in which SeaMex operates is considered to be an indicator of impairment. We have determined the length and severity of the deterioration of market conditions to be representative of an other than temporary impairment. As such we measured and recognized an other than temporary impairment of the investment in SeaMex as at September 30, 2016. The fair value was derived using an income approach, which discounts future free cash flows (“DCF model”). The estimated future free cash flows associated with the investment were primarily based on expectations around applicable day rates, drilling unit utilization, operating costs, capital and long-term maintenance expenditures and applicable tax rates. The cash flows were estimated over the remaining useful economic lives of the underlying assets but no longer than 30 years in total, and discounted using an estimated market participant weighted average cost of capital of 11% . The DCF model derived an enterprise value of the investments, after which associated debt was subtracted to provide equity values. The carrying value of the investment was found to exceed the fair value by $76 million . We recognized this impairment of the investments within “Loss on impairment of Investments” in the Consolidated Statement of Operations. Itaunas Drilling, Camburi Drilling, and Sahy Drilling - Impairment of investment in Joint Venture Itaunas Drilling BV, Camburi Drilling BV and Sahy Drilling BV are joint ventures which each have a contract to construct one drillship. The joint ventures are owned 70% by Sete International (a subsidiary of Sete Brasil Participacoes SA) and 30% by us. During the year ended December 31, 2016, due to the deteriorating market conditions in the offshore drilling industry, the uncertainty around the financial condition of Sete Brasil Participacoes SA, and the uncertainty around the recoverability of the investments, we recognized an other than temporary impairment of $13 million to write down the value of these investments to nil. We recognized this impairment within “Loss on impairment of investments” in the Consolidated Statement of Operations. Impairment loss recognized for the year ended December 31, 2015 Seadrill Partners - Common Units - Impairment of marketable securities At September 30, 2015 management determined that the investment in Seadrill Partners’ common units was other than temporarily impaired due to the length and severity of the reduction in value below historic cost. As a result we impaired the investment, recognizing an impairment charge of $574 million within “Loss on impairment of investments.” This impairment charge represents a reclassification of losses previously recognized within Other Comprehensive Income. The amount reclassified out of "Accumulated other comprehensive income" into earnings was determined on the basis of average cost. Seadrill Partners - Subordinated units and direct ownership interests - Impairment of Equity Method Investment As at September 30, 2015, the carrying value of the subordinated units was found to exceed the fair value by $125 million , and the carrying value of the direct ownership interests was found to exceed the fair value by $302 million . We recognized this impairment of the investments within “Loss on impairment of Investments” in the Consolidated Statement of Operations. The assumptions used in the DCF model were derived from unobservable inputs (classified as level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. Seadrill Partners - Member interest - Impairment of Cost method investments The reduction in value of the Seadrill Partners Common Units was determined to be an indicator of impairment of the Seadrill member interest. The fair value was determined using the Monte Carlo model, updated for applicable assumptions as at September 30, 2015. The carrying value of the investment was found to exceed the fair value by $106 million . We recognized this impairment within “Loss on impairment of investments” in the Consolidated Statement of Operations. The assumptions used in the Monte Carlo model were derived from both observable and unobservable inputs (classified as level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. SapuraKencana - Impairment of marketable securities During the period since September 30, 2014, to September 30, 2015, SapuraKencana’s share price fell by approximately 45% as a result of deteriorating market conditions in the oil and gas industry. Between June 30, 2015 and September 30, 2015, the value of the investment fell by approximately 20% , as a result of the declining share price and USD:MYR exchange rate. At September 30, 2015, management determined that the investment in SapuraKencana was other than temporarily impaired due to the length and severity of the reduction in value below historic cost. As a result we impaired the investment, recognizing an impairment charge of $167 million within “Loss on impairment of investments”. This impairment charge represents a reclassification of losses previously recognized within Other Comprehensive Income. The amount reclassified out of "Accumulated other comprehensive income" into earnings was determined on the basis of average cost. During the period to December 31, 2015 we recognized an additional net impairment charge to bring the carrying value of the asset to the realizable value of $195 million . The resulting net impairment was a loss of $ 11 million , which was recognized within "Loss on impairments of investments" in the Consolidated Statement of Operations. As a result, the total impairment charge recognized for the period to December 31, 2015 was $178 million . On April 27, 2016 , we sold our entire shareholding in SapuraKencana for net proceeds of $ 195 million , net of transaction costs. Investment in associated companies We have the following investments that are or have been recorded using the equity method for the periods presented in these Consolidated Financial Statements: Ownership percentage December 31, 2017 December 31, 2016 December 31, 2015 Archer Limited ("Archer") Note 1 39.7 % 39.9 % Seabras Sapura Participacoes Ltda ("Seabras Sapura Participacoes") 50.0 % 50.0 % 50.0 % Seabras Sapura Holding GmbH ("Seabras Sapura Holding") 50.0 % 50.0 % 50.0 % Itaunas Drilling B.V. ("Itaunas Drilling") 30.0 % 30.0 % 30.0 % Camburi Drilling B.V. ("Camburi Drilling") 30.0 % 30.0 % 30.0 % Sahy Drilling B.V. ("Sahy Drilling") 30.0 % 30.0 % 30.0 % Seadrill Partners ("SDLP") Note 2 Note 2 Note 2 SeaMex Ltd. ("SeaMex") 50.0 % 50.0 % 50.0 % (1) As part of their financial restructuring, Archer completed two share issuances in March and April 2017, which diluted Seadrill's ownership interest to 15.7% as at December 31, 2017 . In April 2017, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized it as an available-for-sale security. (2) As at the deconsolidation date of Seadrill Partners on January 2, 2014, we recognized our ownership interests in Seadrill Partners and direct ownership interests in Seadrill Partners subsidiaries, at fair value at the date of deconsolidation. Refer to the Seadrill Partners paragraph below for additional information. At year-end the book values of our investment in associated companies are as follows: (In US$ millions) December 31, 2017 December 31, 2016 Archer (1) N/A — Seabras Sapura Participacoes 63 47 Seabras Sapura Holding 290 227 Itaunas Drilling — — Camburi Drilling — — Sahy Drilling — — Seadrill Partners - Total direct ownership interests 857 1,537 Seadrill Partners - Subordinated units 97 157 Seadrill Partners - Seadrill member interest and IDRs (2) 64 64 Seamex Ltd. 102 136 Total 1,473 2,168 (1) In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized it as an available-for-sale security. (2) The Seadrill Partners - Seadrill member interest and Incentive Distribution Rights (“IDR’s”) are accounted for as cost-method investments on the basis that they do not represent common stock interests and their fair value is not readily determinable. The investments are held at cost and not subsequently re-measured. For more details on the deconsolidation of Seadrill Partners see Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information. Quoted market prices for all of our other equity investments are not available because, other than Seadrill Partners Common Units, these companies are not publicly traded. Seadrill Partners subordinated units are not tradable and hence have no quoted market price. Archer Archer is a company listed on the Oslo Stock Exchange and provides drilling and well services. Prior to February 2011, Archer was a consolidated subsidiary. In February 2011, we deconsolidated Archer and as a result accounted for our interest as an investment in an associated company. On February 8, 2013, Seadrill were allocated 82,003,000 shares in the private placement of Archer, amounting to a value of $98 million . In addition, as consideration for acting as an underwriter to the placement, we received another 2,811,793 shares, amounting to a value of $3 million . The consideration for the shares was settled against the existing $55 million loan to Archer, with the remainder of the consideration funded by a $43 million loan from Archer, which was repaid on February 27, 2013. As part of their financial restructuring, Archer completed two share issuances in March and April 2017, which diluted Seadrill's ownership interest in Archer to 15.7% as at December 31, 2017 . The restructuring also resulted in financial guarantees provided by Seadrill being settled in April and June 2017 and related party loan arrangements with Seadrill being significantly reduced. In April 2017, we concluded that we no longer had significant influence over Archer's financial and operating decisions, primarily as a result of the reduction in our shareholding and the significant reduction in our interests in related debt and guarantees. Our investment in Archer was therefore derecognized as an investment in associate and recognized as an available-for-sale security at the closing carrying value of the equity investment in associate, nil . A $10 million accumulated other comprehensive income gain related to the equity method investment was recycled to the Consolidated Statement of Operations. For transactions and balances with Archer, refer to Note 30 "Related party transactions" for more information. Seabras Sapura Participacoes and Seabras Sapura Holding Seabras Sapura Participacoes S.A. is a company incorporated in Brazil, which is currently constructing one pipe-laying vessel. It is 50% owned by TL Offshore Sdn. Bhd., a subsidiary of SapuraKencana, and 50% owned by Seadrill. Seabras Sapura Holding GmbH is a company incorporated in Austria, which is owns five pipe-laying vessels. It is 50% owned by TL Offshore Sdn. Bhd. and 50% owned by Seadrill. For transactions and balances with Seabras Sapura Participacoes and Seabras Sapura Holding, please refer to Note 30 "Related party transactions". Itaunas Drilling, Camburi Drilling, and Sahy Drilling Itaunas Drilling BV is a company incorporated in Holland, which has contracted to construct a drillship. It is 70% owned by Sete International GmbH, (a subsidiary of Sete Brasil Participacoes SA), and 30% owned by Seadrill. Camburi Drilling BV is a company incorporated in Holland, which has contracted to construct a drillship. It is 70% owned by Sete International GmbH and 30% owned by Seadrill. Sahy Drilling BV is a company incorporated in Holland, which has contracted to construct a drillship. It is 70% owned by Sete International GmbH and 30% owned by the Seadrill. During the twelve months ended December 31, 2016, due to the deteriorating market conditions in the offshore drilling industry, the uncertainty around the financial condition of Sete Brasil Participacoes SA, and the uncertainty around the recoverability of the investments, we recognized an other than temporary impairment of $13 million to write down the value of these investments to nil. We have recognized this impairment within “Loss on impairment of investments” in the Consolidated Statement of Operations. Refer to Note 8 "Impairment loss on marketable securities and investments in associated companies" for more information. Seadrill Partners Seadrill’s investment in Seadrill Partners accounted for under the equity method is comprised of the following: (a) Subordinated units - our holdings of subordinated units of Seadrill Partners are accounted for under the equity method on the basis that the subordinated units are considered to be ‘in-substance common stock’. The subordination period will end on the satisfaction of various tests as prescribed in the Operating Agreement of Seadrill Partners. Upon the expiration of the subordination period, the subordinated units will convert into Common Units. (b) Direct Ownership interests - Seadrill holds ownership interests in the following entities controlled by Seadrill Partners as at December 31, 2017 : i. 42% in Seadrill Operating LP : Seadrill Operating LP is a limited partnership and is controlled by its General Partner, Seadrill Operating GP LLC, which is wholly owned by Seadrill Partners. ii. 49% Seadrill Capricorn Holdings LLC : Seadrill Capricorn Holdings LLC is a limited liability company. There is only one class of member interest which is deemed to represent voting common stock. iii. 39% in Seadrill Deepwater Drillship Ltd and 49% indirect interest in Seadrill Mobile Units (Nigeria) Ltd. : Both entities are limited companies and only have one class of stock, which is deemed to represent voting common stock. All of our direct ownership interests are accounted for under the equity method as we are deemed to have significant influence over these entities through its voting rights and by virtue of Seadrill’s representation on the Board of Seadrill Partners. Purchase of 10% interest in Seadrill Mobile Units Nigeria Limited On December 5, 2016 , our wholly owned subsidiary Seadrill UK Ltd. acquired a 10% interest that an unrelated party, HH Global Alliance Investments Limited (“HHL”) held in Seadrill Mobile Units (Nigeria) Ltd, the service company for West Capella , for a notional value of $6.6 million . Following the completion of this transaction Seadrill UK Ltd. owns 49% of Seadrill Mobile Units Nigeria Limited, with the remaining 51% being owned by subsidiaries of Seadrill Partners. Simultaneously HHL acquired from Seadrill UK Ltd. a 49% interest in Seadrill Nigeria Operations Limited, the service company for West Jupiter for a notional value of $6.6 million . The impact of these transactions was to increase Seadrill’s direct ownership interest in Seadrill Partners by $6.6 million , and to recognize HHL’s non-controlling interest in Seadrill Nigeria Operations Ltd of $6.6 million . Impairment During the years ending December 31, 2017 , 2016 and 2015 , we recognized other than temporary impairments on the equity method investments in Seadrill Partners for $805 million , $653 million and $533 million respectively. Refer to Note 8 "Impairment loss on marketable securities and investments in associated companies" for more information. For transactions and balances with Seadrill Partners, please refer to Note 30 "Related party transactions". SeaMex During the year ended December 31, 2014, we entered into a joint venture agreement with an investment fund controlled by Fintech, for the purpose of owning and managing certain jack-up drilling units located in Mexico under contract with Pemex. The transaction was completed on March 10, 2015, when Fintech subscribed for a 50% ownership interest in the joint venture company, SeaMex, which was previously 50% owned by us, and SeaMex simultaneously purchased the jack-up drilling rigs from Seadrill Limited. As a result of the transaction we no longer control the entities that own and operate these jack-up drilling units, and accordingly we have deconsolidated these entities as at March 10, 2015, and has recognized our remaining 50% investment in the joint venture at fair value. The fair value of the retained 50% equity interest in the SeaMex joint venture was determined by reference to the price paid by Fintech to obtain a 50% equity interest in the Disposal group from Seadrill. We accounts for our 50% investment in the joint venture under the equity method. Refer to Note 11 "Disposals of business and deconsolidation of subsidiaries" for further information. During the year ended December 31, 2015 both the JV partners each made an additional $19 million of equity investment in SeaMex while retaining their 50% share in the JV. Impairment During the years ended December 31, 2017 and December 31, 2016 , we recognized other than temporary impairments on the equity method investments in SeaMex Limited for $36 million and $76 million respectively. Refer to Note 8 "Impairment loss on marketable securities and investments in associated companies" for further information. For transactions and balances with SeaMex, refer to Note 30 "Related party transactions". Summary financial information of the equity method investees Summarized Consolidated Balance Sheet information of our equity method investees is as follows: Balance at December 31, 2017 (In US$ millions) Current assets Non-current assets Current liabilities Non-current liabilities Non-Controlling interest Archer N/A N/A N/A N/A N/A Seabras Sapura Participacoes 126 299 131 169 — Seabras Sapura Holding 341 1,331 542 845 — Seadrill Partners 1,214 5,317 546 3,284 1,398 SeaMex 294 1,036 222 666 — Total 1,975 7,983 1,441 4,964 1,398 Balance at December 31, 2016 (In US$ millions) Current assets Non-current assets Current liabilities Non-current liabilities Non-Controlling interest Archer 287 773 313 718 — Seabras Sapura Participacoes 100 317 149 174 — Seabras Sapura Holding 258 1,393 509 988 — Seadrill Partners 1,214 5,567 665 3,580 1,343 SeaMex 296 1,095 145 818 — Total 2,155 9,145 1,781 6,278 1,343 Summarized Consolidated Statement of Operations information for our equity method investees is as follows: Year ended December 31, 2017 (In US$ millions) Operating revenues Net operating income Net income Net income attributable to non-controlling interest Archer N/A N/A N/A — Seabras Sapura Participacoes 76 60 34 — Seabras Sapura Holding 186 184 126 — Seadrill Partners 1,128 464 235 94 SeaMex 239 80 15 — Total 1,629 788 410 94 Year ended December 31, 2016 (In US$ millions) Operating revenues Net operating (loss)/income Net (loss)/income Net income attributable to non-controlling interest Archer 818 (41 ) (166 ) — Seabras Sapura Participacoes 148 46 39 — Seabras Sapura Holding 241 155 89 — Seadrill Partners 1,600 818 546 265 SeaMex 280 119 36 — Total 3,087 1,097 544 265 Year ended December 31, 2015 (In US$ millions) Operating revenues Net operating (loss)/income Net (loss)/income Net income attributable to non-controlling interest Archer 1,321 (13 ) (359 ) — Seabras Sapura Participacoes 53 3 1 — Seabras Sapura Holding 124 76 51 — Seadrill Partners 1,742 844 488 231 Seamex 238 79 24 — Total 3,478 989 205 231 At the year end the share of recorded equity in the statutory accounts of our associated companies were as follows: (In US$ millions) December 31, 2017 December 31, 2016 December 31, 2015 Archer (1) N/A 15 79 Seabras Sapura Participacoes 63 47 24 Seabras Sapura Holding 143 77 19 Seadrill Partners (2) N/A N/A N/A Seamex 221 218 200 Total 427 357 322 (1) In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized as an available-for-sale security. (2) We account for our direct interests in operating subsidiaries of Seadrill Partners, and our ownership of Seadrill Partners Subordinated Units, under the equity method. Our share of Seadrill Partners recorded equity consists of the equity attributable to non-controlling interests in Seadrill Partners, and additionally a proportionate share of equity attributable to Seadrill Partners’ unitholders. The equity attributable to non-controlling interest in Seadrill Partners as at December 31, 2017 was $1,398 million (December 31, 2016: $1,343 million ). Seadrill’s holding in the subordinated units represents 18.0% of the limited partner interests in Seadrill Partners. Total equity attributable to Seadrill Partners' unitholders as at December 31, 2017 was $1,304 million (December 31, 2016: $1,193 million ).

Newbuildings

Newbuildings	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Newbuildings	Newbuildings As part of the global settlement reached under the Plan, four contracts with two newbuild counterparties were rejected and terminated. In consideration for the contract rejections, the newbuild counterparties filed claims with the Bankruptcy Court and were included as Commitment Parties under the amended Investment Agreement as well as received certain pro rata share of established cash pools for general unsecured creditors. Refer to Note 3 - "Chapter 11 Proceedings" for further information. (In US$ millions) December 31, 2017 December 31, 2016 Opening balance 1,531 1,479 Additions 5 12 Capitalized interest and loan related costs 28 40 Disposals (1) (620 ) — Impairment (2) (696 ) — Closing balance 248 1,531 (1) In July 2017, Sevan Drilling and Cosco reached agreement to defer the Sevan Developer delivery period until June 30, 2020. The contract amendment included a termination clause for Cosco and therefore it was deemed that Sevan had lost control of the asset. The Newbuild asset and corresponding construction obligation were derecognized. Refer to Note 6 - Loss on disposals for further information. (2) As part of the Chapter 11 proceedings, the Debtors negotiated and announced a global settlement with various creditors, including Samsung Heavy Industries Co., Ltd. ("Samsung") and Daewoo Shipbuilding & Marine Engineering Co., Ltd ("DSME"). The global settlement included an agreement regarding the allowed claim of the newbuild shipyards Samsung and DSME, and the Debtors’ rejection and recognized termination of the newbuild contracts for the West Dorado, West Draco, West Aquila and the West Libra . As the Plan anticipates the rejection and termination of the newbuild contracts we have recognized an impairment of the newbuild assets related to the West Dorado, West Draco, West Aquila and the West Libra, totaling $696 million , in the year ended December 31, 2017.

Drilling units

Drilling units	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Drilling units	Drilling units (In US$ millions) December 31, 2017 December 31, 2016 Cost 17,335 17,753 Accumulated depreciation (1) (4,119 ) (3,477 ) Net book value 13,216 14,276 (1) Depreciation and amortization expense was $779 million , $801 million and $761 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Equipment

Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Equipment	Equipment Equipment consists of office equipment, software, furniture and fittings. (In US$ millions) December 31, 2017 December 31, 2016 Cost 84 77 Accumulated depreciation (1) (55 ) (36 ) Net book value 29 41 (1) Depreciation and amortization expense was $19 million , $9 million and $18 million for the years ended December 31, 2017 and 2016 and 2015 , respectively.

Goodwill and other intangible a

Goodwill and other intangible assets and liabilities	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and other intangible assets and liabilities	Goodwill and other intangible assets and liabilities Goodwill The goodwill balance and changes in the carrying amount is as follows: (In US$ millions) December 31, 2017 December 31, 2016 Opening balance Goodwill 795 795 Accumulated impairment losses (795 ) (795 ) Total opening goodwill — — Disposals of businesses and deconsolidation of subsidiaries (Note 11) — — Impairment of goodwill — — Closing balance Goodwill 795 795 Accumulated impairment losses (795 ) (795 ) Total closing goodwill — — Goodwill impairment for the year ended December 31, 2015 During the period between June 30, 2015 and September 30, 2015 the Company’s share price fell by 43% from $10.34 to $5.90 (based on the closing spot price), and by 34% , from $12.04 to $7.96 (based on the average trailing three month basis), partly as a result of deteriorating market conditions in the oil and gas industry and supply and demand conditions in the ultra-deepwater offshore drilling sector. As a result management determined that the goodwill assigned to the Company’s floaters reporting unit was likely to be impaired, and performed a quantitative impairment test as at September 30, 2015. As at September 30, 2015 an impairment test was conducted, and it resulted in the Company recognizing an impairment loss of $563 million relating to the floaters reporting unit which represented all of the goodwill attributable to that reporting unit. Following the impairment, the Company no longer retains any goodwill balance. The impairment is a result of deteriorating market conditions and the Company’s outlook on expected conditions through the current down-cycle. The impairment charge was allocated between the parent and non-controlling interests based upon the non-controlling interests’ share in each drilling unit within the floater segment. The overall charge to the reporting unit was first allocated to each drilling unit based upon the relative fair values of those drilling units. The percentage non-controlling interest in each drilling unit was then applied to the allocated charge in order to determine the portion attributable to non-controlling interests. The total impairment allocated to the non-controlling interest was $95 million . The estimated fair value of the reporting unit was derived using an income approach, using discounted future free cash flows. The Company’s estimated future free cash flows are primarily based on its expectations around day rates, drilling unit utilization, operating costs, capital and long term maintenance expenditures and applicable tax rates. The cash flows are estimated over the remaining useful economic lives of the assets but no longer than 30 years in total, and discounted using an estimated market participant weighted average cost of capital of 10% . The assumptions used in the Company’s estimated cash flows were derived from unobservable inputs (level 3) and are based on management’s judgments and assumptions available at the time of performing the impairment test. Intangibles Intangible liabilities relate to unfavorable contracts which are recorded at fair value at the date of acquisition. The amounts recognized represent the net present value of the existing contracts at the time of acquisition compared to the current market rates at the time of acquisition, discounted at the weighted average cost of capital. The estimated unfavorable contract values have been recognized and amortized over the terms of the contracts, ranging from two to five years. The gross carrying amounts and accumulated amortization were as follows: December 31, 2017 December 31, 2016 (In US$ millions) Gross carrying amount Accumulated amortization Net carrying amount Gross carrying amount Accumulated amortization Net carrying amount Unfavorable contracts - intangible liabilities Balance at the beginning of the period 444 (378 ) 66 444 (313 ) 131 Amortization of unfavorable contracts — (43 ) (43 ) — (65 ) (65 ) Balance at the end of the period 444 (421 ) 23 444 (378 ) 66 There have been no favorable contracts recognized. Unfavorable contracts have been recognized within "Other current liabilities" within the Consolidated Balance Sheet. We amortize unfavorable contracts as revenue over the contract term. This amortization is recognized within "Other revenues" in the Consolidated Statement of Operations. The table below shows the amounts relating to unfavorable contracts that is expected to be amortized over the next five years: Year ended December 31, (In US$ millions) 2018 2019 2020 2021 2022 Total Amortization of unfavorable contracts 23 — — — — 23

Other non-current assets

Other non-current assets	12 Months Ended
	Dec. 31, 2017
Other Assets, Noncurrent Disclosure [Abstract]
Other non-current assets	Other non-current assets Other non-current assets consist of the following: (In US$ millions) December 31, 2017 December 31, 2016 Deferred tax effect of internal transfer of assets 75 84 Deferred mobilization costs 5 14 Other 1 3 Total other non-current assets 81 101

Long-term debt

Long-term debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Long-term debt	Long-term debt As at December 31, 2017 and 2016 , we had the following debt: (In US$ millions), unless stated otherwise December 31, 2017 December 31, 2016 Secured credit facilities $1,500 million facility (1) 1,112 1,219 $1,350 million facility (1) 931 1,046 $2,000 million facility (NADL) (1) 897 1,033 $1,750 million facility (Sevan Drilling) (1) 856 945 $950 million facility (1) 558 622 $1,450 million facility (1) 318 353 $450 million Eminence facility (1) 261 278 $360 facility (Asia Offshore Drilling) 210 237 $300 million facility (1) 142 162 $400 million facility (1) 133 190 $450 million facility (2015) (1) 101 175 $440 million facility (1) 62 190 Total secured credit facilities 5,581 6,450 Ship Finance Loans $390 million facility (SFL Deepwater) 226 248 $375 million facility (SFL Hercules) 251 279 $475 million facility (SFL Linus) 309 356 Total Ship Finance Loans 786 883 Unsecured bonds $1,000 million bond (2) 843 843 NOK1,800 million bond (2) 231 210 $500 million bond (2) 479 479 NOK1,500 million bond (NADL) (2) 182 165 $ 600 million bond (NADL) (2) 413 413 SEK 1,500 million bond (2) 186 165 Total unsecured bonds 2,334 2,275 Total debt principal 8,701 9,608 Less: Debt balance held as subject to compromise (7,705 ) — Debt balance not subject to compromise 996 9,608 Less: current interest bearing debt not subject to compromise (511 ) (3,230 ) Long-term interest bearing debt not subject to compromise 485 6,378 (1) Denotes impaired secured credit facilities that were reclassified to "Liabilities subject to compromise" on September 12, 2017 (2) Denotes unsecured bonds that were reclassified to "Liabilities subject to compromise" on September 12, 2017 The Debtors filing of Bankruptcy on the Petition Date constituted an event of default under our secured credit facilities and unsecured bond facilities and were reported as "Liabilities subject to compromise" on the Consolidated Balance Sheets at December 31, 2017 . During bankruptcy proceedings we continue to make interest payments on the secured credit facilities. These are treated as adequate protection payments which are recognized as a reduction in the principal balance of secured credit facilities held within "Liabilities subject to compromise" in the Consolidated Balance Sheets. $81 million has been recognized as adequate protection payments from Petition date to December 31, 2017 . The Debtors have discontinued recording interest on unsecured bond facilities classified as liabilities subject to compromise from the Petition Date. On filing for Chapter 11, $66 million of unamortized debt issuance costs on the impaired secured credit facilities and unsecured bonds were expensed and recognized within "Reorganization items, net" in the Consolidated Statement of Operations. Details of the debt issuance costs netted against the non-impaired current and long-term debt for each of the periods presented are shown below. Outstanding balance as at December 31, 2017 (In US$ millions) Principal outstanding Less: Debt issuance costs Total debt Debt due within one year 511 (2 ) 509 Long-term debt 485 — 485 Debt held as subject to compromise 7,705 — 7,705 Total 8,701 (2 ) 8,699 Outstanding debt as at December 31, 2016 (In US$ millions) Principal outstanding Less: Debt issuance costs Total debt Debt due within one year 3,230 (35 ) 3,195 Long-term debt 6,378 (59 ) 6,319 Total 9,608 (94 ) 9,514 The outstanding debt as at December 31, 2017 is repayable as follows: (In US$ millions) December 31, 2017 2018 511 2019 485 Total debt principal (1) 996 (1) Excludes impaired secured debt and unsecured bonds held within "Liabilities subject to compromise" Credit facilities subject to compromise The following facilities were held within Liabilities Subject to Compromise as at December 31, 2017 . $2,000 million senior secured credit facility In April 2011 , North Atlantic Drilling Ltd., or “NADL”, our majority owned subsidiary, entered into a $2,000 million senior secured credit facility with a syndicate of banks to partly fund the acquisition of six drilling units from Seadrill, which have been pledged as security. The net book value at December 31, 2017 of the units pledged as security is $1,810 million . The facility has a six year term and bears interest at LIBOR plus 2.00% per annum. As at December 31, 2017 , the outstanding balance was $897 million , as compared to $1,033 million in 2016 . The outstanding balance represents the final balloon payment of $908 million offset by adequate protection payments made after September 12, 2017 of $11 million . On April 28, 2016 , we executed maturity extension agreements to extend the maturity of this facility from April 15, 2017 to June 30, 2017. On April 4, 2017, we obtained an extension agreement to extend the maturity until September 14, 2017. This remains outstanding as at December 31, 2017 as a result of the RSA entered into on September 12, 2017. As at December 31, 2016 , $50 million was undrawn under this facility, which bears a commitment fee of 40% of the margin. In April 2017 the undrawn portion of the revolving facility was cancelled. The facility contains a loan-to-value clause, which could require NADL, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 135% of the outstanding loan, however following the amendment made in April 2017 , this covenant was suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or is, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. $400 million senior secured credit facility In December 2011 , we entered into a $400 million senior secured credit facility with a syndicate of banks. The jack-up rigs West Cressida , West Callisto , West Leda and West Triton have been pledged as security. The net book value at December 31, 2017 of the units pledged as security is $507 million . The facility has a five year term and bears interest of LIBOR plus 2.50% per annum. In May 2017, we completed the sale of West Triton to Shelf Drilling. Shelf Drilling subsequently repaid the tranches relating to the West Triton in full, amounting to $47 million . As at December 31, 2017 , the outstanding balance was $133 million , which represents balloon payment of $135 million offset by adequate protection payments made after September 12, 2017 of $2 million . We do not have any undrawn capacity on this facility as at December 31, 2017 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 150% of the outstanding loan, however following the amendment made in April 2017 , this covenant was suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or is, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. On April 28, 2016 we executed maturity extension agreements to extend the maturity of this facility from December 8, 2016 to May 31, 2017 . On April 4, 2017, we obtained an extension agreement to further extend the maturity until August 31, 2017. On July 26, 2017 this was further extended to September 14, 2017. This remains outstanding as at December 31, 2017 as a result of the RSA entered into on September 12, 2017. The outstanding balance on the credit facility is $133 million as at December 31, 2017 . $440 million secured credit facility In December 2012 , we entered into a $440 million secured credit facility with a syndicate of banks to fund the delivery of two tender rigs and two jack-up drilling rigs. As at December 31, 2016 we had drawn $320 million on the facility and the T-15, T-16 , and West Telesto had been pledged as security, while the tranche for the West Oberon was cancelled due to other funding opportunities for this rig. The tender rigs T-15 and T-16 were sold to Seadrill Partners during 2013, and subsequently we entered into a back to back rig financing agreements with Seadrill Partners for the corresponding portions of the secured credit facility for $101 million and $98 million respectively. In August 2017, Seadrill Partners amended certain credit facilities to insulate itself from us. This resulted in a $109 million repayment in respect to this facility. See Note 30 "Related party transactions" for further details on related party transactions. The total net book values as at December 31, 2017 of the West Telesto , which is pledged as security, was $188 million . The facility bears interest at LIBOR plus 3.25% per annum and is repayable over a term of 5 years . The outstanding balance as at December 31, 2017 was $62 million , which represents balloon payment of $64 million offset by adequate protection payments made after September 12, 2017 of $2 million . We do not have any undrawn capacity on this facility as at December 31, 2017 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 135% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or is, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. $1,450 million senior secured credit facility In March 2013 , we entered into a $1,450 million senior secured credit facility with a syndicate of banks and export credit agencies. The West Auriga , West Vela , and West Tellus were pledged as security. The facility has a final maturity in 2025 , with the exception of a commercial tranche of $203 million due for renewal in 2018 , and bears an interest of LIBOR plus a margin, inclusive of the guarantee fee, in the range of 2.70% to 3.00% . Due to the sale of the West Auriga and West Vela to Seadrill Partners in 2014, the tranches relating to these rigs were recognized by Seadrill Partners. In August 2017, Seadrill Partners completed amendments to this facility to insulate itself from Seadrill Limited and therefore Seadrill no longer provided an indemnity to Seadrill Partners for any payments or obligations related to this facility that are not related to the West Auriga or West Vela . The total amount owed as at December 31, 2017 is $318 million (compared to $695 million as at December 31, 2016 ) which fully relates to Seadrill and the West Tellus ( $353 million as at December 31, 2016 ). As at December 31, 2017 the net book value of the West Tellus was $615 million . We do not have any undrawn capacity on this facility as at December 31, 2017 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 125% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or is, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. $300 million senior secured credit facility In July 2013 , we entered into a $300 million senior secured credit facility with a syndicate of banks and export credit agencies. The West Tucana and West Castor were pledged as security. The facility bears interest of LIBOR plus a margin of 3.00% , which includes the guarantee fee paid to the credit export agency. The facility matures in 2023 , however the facility may become payable in full in 2018 if the commercial tranche which expires after 5 years is not renewed. As at December 31, 2017 the net book values of the West Tucana and West Castor were $181 million and $186 million respectively. We do not have any undrawn capacity on this facility as at December 31, 2017 . As at December 31, 2017 the outstanding balance was $142 million as compared to $162 million as at December 31, 2016 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 135% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or is, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. $1,750 million secured credit facility In September 2013 subsidiaries of Sevan Drilling entered into a $1,750 million bank facility with a syndicate of banks and export credit agencies. The facility consists of two tranches in the amounts of $1,400 million and $350 million . On October 23, 2013 the first tranche of $1,400 million was drawn and was used to repay the existing credit facilities related to Sevan Driller and Sevan Brasil and to settle the remaining installment and other amounts for the delivery of Sevan Louisiana . The Sevan Driller , Sevan Brasil and Sevan Louisiana have been pledged as security. In December 2014 the $350 million tranche relating to the Sevan Developer was cancelled at our request as a consequence of the deferral agreement made with Cosco, and the borrowing entity relating to the Sevan Developer was released from its obligations under this facility. The facility has a maturity in September 2018 and bears interest of LIBOR plus a margin of 2.85% , which includes the guarantee fee paid to the credit export agency. As at December 31, 2017 the net book values of the Sevan Driller , Sevan Brasil and Sevan Louisiana were $525 million , $552 million and $648 million respectively. We do not have any undrawn capacity on this facility as at December 31, 2017 . As at December 31, 2017 , the outstanding balance was $856 million as compared to $945 million as at December 31, 2016 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 110% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or is, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. $450 million senior secured credit facility In December 2013 , we entered into a $450 million senior secured facility with a syndicate of banks. The West Eminence has been pledged as security, and bears interest of LIBOR plus a margin of 1.75% and was due to mature in June 2016 . As at December 31, 2017 the net book value of the West Eminence was $508 million . As at December 31, 2017 , the outstanding balance was $261 million as compared to $278 million as at December 31, 2016 . We do not have any undrawn capacity on this facility as at December 31, 2017 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 130% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or is, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. On April 28, 2016 we executed maturity extension agreements to extend the maturity of this facility from June 20, 2016 to December 31, 2016 . I n addition, the margin was increased to 2.50% , effective June 2016 . On November 16, 2016 , the maturity was extended until April 30, 2017 . On April 4, 2017, the maturity was extended until August 15, 2017. On August 15, 2017, the maturity was extended to September 14, 2017. This remains outstanding as at December 31, 2017 as a result of the RSA entered into on September 12, 2017. The outstanding balance on the credit facility is $261 million as at December 31, 2017 . $1,500 million senior secured credit facility (2014) In July 2014 , we entered into a $1,500 million senior secured credit facility with a syndicate of banks to finance three newbuilds, the West Saturn, West Neptune and West Jupiter, which are pledged as security. The net book value at December 31, 2017 of the units pledged as security is $1,831 million . The facility bears interest at LIBOR plus a margin of between 1.7% and 2.38% per annum, plus certain export credit agency fees, and is repayable over a term of 12 years. The loan includes a Commercial Interest Reference Rate (CIRR) tranche with Eksportkreditt Norge ASA, the Norwegian export credit agency, that bears fixed interest at 2.38% per annum. If the commercial tranche of $300 million , which has a balloon payment of $175 million , does not get refinanced to the satisfaction of the remaining lenders after five years, the remaining tranches also become due after five years. We do not have any undrawn capacity on this facility as at December 31, 2017 . As at December 31, 2017 , the outstanding balance was $1,112 million as compared to $1,219 million as at December 31, 2016 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below an average of 122% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or is, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. $1,350 million senior secured credit facility In August 2014 , we entered into a $1,350 million senior secured credit facility with a syndicate of banks. The facility consists of a term loan facility for $675 million and a revolving credit facility in an amount up to $675 million . The West Pegasus , West Gemini and West Orion were pledged as security. The total net book value at December 31, 2017 of the units pledged as security is $1,570 million . The facility bears interest at LIBOR plus a margin of 2% per annum, and is repayable in quarterly installments over a term of five years. The revolver is fully repayable at the final maturity date. The revolver facility was fully drawn and we do not have any undrawn capacity as at December 31, 2017 . As at December 31, 2017 , the outstanding balance was $931 million as compared to $1,046 million as at December 31, 2016 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 120% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or is, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. $950 million senior secured credit facility In January 2015 we entered into a $950 million senior secured credit facility with a syndicate of banks and export credit agencies to fund the delivery of the West Carina and to refinance our indebtedness related to the West Eclipse . The facility comprises of a $60 million term loan, a $250 million revolving facility and a $190 million Export Credit Agency (ECA) facility for the West Carina; and a $225 million term loan and a $225 million revolving facility for the West Eclipse . The term loans and revolving credit facilities bear interest at LIBOR plus 2.00% and the ECA facility has a CIRR fixed interest rate of 2.12% . In addition the ECA facility for the West Carina has a guarantee fee to the export credit agency of 1.30% . We have entered into a floating swap agreement to counter this fixed payment, meaning we pay floating interest on this tranche, however this agreement was terminated on September 13, 2017 after filing for Chapter 11. The West Carina term loan and revolving credit facility have a 5 year maturity and a 12 year profile, with a balloon payment of $187 million in year 5 . The West Carina ECA facility has a 12 year maturity and a 12 year profile. The West Eclipse term loan has a 5 year maturity and a 10 year profile. The West Eclipse revolving credit facility has a maturity of 5 years and is non-amortizing, with a balloon payment of $225 million in year 5 . If the commercial facilities are not refinanced satisfactorily after 5 years then the ECA facility also becomes due. The net book value of the rigs pledged as security as at December 31, 2017 is $1,256 million . The total outstanding balance as at December 31, 2017 was $558 million ( December 31, 2016 : $622 million ). In April 2017 the undrawn portion of the revolving facility of $171 million was cancelled, of which $100 million related to the West Eclipse and $71 million related to the West Carina . We do not have any undrawn capacity on this facility as at December 31, 2017 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 120% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or are, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. $450 million senior secured credit facility (2015) In August 2015 we entered into a $450 million senior secured credit facility with a syndicate of banks. The West Freedom, West Mischief, West Vigilant, West Resolute, West Prospero, and the West Ariel were pledged as security. The net book value of the rigs pledged as security as at December 31, 2017 is $527 million . The loan bears interest at a rate of LIBOR plus 2.5% . The loan has a 5 year maturity and an 8.5 year profile with a balloon payment at the end of year 5 . In May 2017, we completed the sale of West Resolute to Shelf Drilling. In September 2017, we completed the sale of West Mischief to Shelf Drilling. Shelf Drilling subsequently repaid $54 million on the facility, representing the tranches relating to the West Resolute and West Mischief . The total outstanding balance as at December 31, 2017 was $101 million ( December 31, 2016 : $175 million ). The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 150% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or are, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. In April 2017 the undrawn portion of the revolving facility, totaling $165 million was canceled. We do not have any undrawn capacity on this facility as at December 31, 2017 . Credit facilities not subject to compromise $360 million senior secured credit facility In April 2013 , our majority owned subsidiary AOD entered into a $360 million senior secured credit facility with a syndicate of banks. The facility is available in three equal tranches of $120 million , with each tranche relating to AOD 1, AOD 2 and AOD 3 , which have been pledged as security. The loan has a five year maturity from the initial borrowing date, and bears interest of LIBOR plus 2.75% . As at December 31, 2017 the rigs have a net book value of $210 million , $201 million and $209 million respectively. We do not have any undrawn capacity on this facility as at December 31, 2017 . As at December 31, 2017 the outstanding balance was $210 million as compared to $237 million as at December 31, 2016 . The facility contains a loan-to-value clause, which could require us, to post additional collateral or prepay a portion of the outstanding borrowings should the market value of the drilling units fall below 120% of the outstanding loan, however following the amendment made in April 2017 , this covenant has been suspended. This facility is not subject to compromise as the AOD subsidiary did not file for bankruptcy under Chapter 11, however the covenant terms under the RSA are still applicable. As part of the RSA entered into on September 12, 2017, the lenders have agreed to waive any breach of, or default under, our debt agreements after this date, which arise as a result of or are, directly or indirectly, related to the commencement of Chapter 11 proceedings or any of the steps contemplated in, or to be undertaken pursuant to, the RSA including any failure to comply with any of the financial covenants in the debt agreement. Ship Finance International Limited (“Ship Finance”) Loans The following loans relate to the Ship Finance entities that we consolidate into the Consolidated Financial Statements as Variable Interest Entities ("VIEs"). Refer to Note 34 "Variable interest entities" for more information. These facilities are not subject to compromise as the SFL entities did not file for bankruptcy under Chapter 11. SFL Hercules Ltd In May 2013 , SFL Hercules Ltd entered into a $375 million facility, with a syndicate of banks and financial institutions. The facility is secured by the West Hercules , which has a net book value of $508 million as at December 31, 2017 . The new facility has a term of six years and bears interest of LIBOR plus a margin of 2.75% . During the year ended December 31, 2016 , SFL Hercules Ltd drew down $50 million on its revolving credit tranche. Subsequently the VIE repaid balances with Ship Finance, a related party to Seadrill, thus reducing the consolidated related party net debt. As at December 31, 2017 , the outstanding balance under the facility was $251 million , compared to $279 million as at December 31, 2016 . SFL Hercules Ltd has no undrawn capacity on this facility at December 31, 2017 . SFL Deepwater Ltd In October 2013 , SFL Deepwater Ltd entered into a $390 million facility with a syndicate of banks and financial institutions. The facility is secured by the West Taurus , which has a net book value of $385 million as at December 31, 2017 . The new facility has a term of five years and bears interest of LIBOR plus a margin of 2.50% . During the year ended December 31, 2016 , SFL Deepwater Ltd drew down $50 million on its revolving credit tranche. Subsequently the VIE repaid balances with Ship Finance, a related party to Seadrill, thus reducing the consolidated related party net debt. As at December 31, 2017 , the outstanding balance under the facility was $226 million , compared to $248 million as at December 31, 2016 . SFL Deepwater Ltd has no undrawn capacity on this facility as at December 31, 2017 . SFL Linus Ltd In October 2013 , SFL Linus Ltd entered into a $475 million secured term loan and revolving credit facility with a syndicate of banks to fund the acquisition of West Linus , which has been pledged as security and has a net book value of $515 million as at December 31, 2017 . The facility was fully drawn on February 18, 2014 , on the date of delivery of West Linus . The facility bears interest of LIBOR plus 2.75% and matures in June 2019 . During the year ended December 31, 2016 , SFL Linus Ltd drew down $50 million on its revolving credit tranche. Subsequently the VIE repaid balances with Ship Finance, a related party to Seadrill, thus reducing the consolidated related party net debt. As at December 31, 2017 , the outstanding balance under the facility was $309 million compared to $356 million as at December 31, 2016 . SFL Linus has no undrawn capacity on this facility at December 31, 2017 . Unsecured Bonds subject to compromise The following unsecured bonds are included in liabilities subject to compromise in the Consolidated Balance Sheet as of December 31, 2017 . $1,000 million fixed interest bond In September 2012 , we raised $1,000 million through the issue of a 5 year bond which was due to mature in September 2017 . This remains outstanding as at December 31, 2017 as a result of the RSA entered into on September 12, 2017. Interest on the bonds bears a fixed interest rate of 5.625% per annum, payable semi-annually in arrears. The interest rate increased to 6.125% in March 2014 as we remained unrated. During the year ended December 31, 2015 , we repurchased $52 million (par value) of the $1,000 million senior unsecured bond, recognizing a gain on debt extinguishment of $8 million in our Consolidated Statement of Operations. In May 2016 , Seadrill Limited entered into a privately negotiated exchange agreement with certain holders of its outstanding 5.625% (subsequently increased to 6.125% ) Senior Notes due 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 8,184,340 new shares of its common stock, par value $2.00 per share, in exchange for $55.0 million principal amount of the 2017 Notes in accordance with Section 3(a)(9) of the U.S. Securities Act of 1933, as amended. Settlement occurred on May 20, 2016 , upon which we had a total of 500,944,280 shares of its common stock issued and outstanding. In June 2016 , Seadrill Limited entered into a privately negotiated exchange agreement with certain holders of its outstanding 5.625% (subsequently increased to 6.125% ) Senior Notes due 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 7,500,000 n

Other current liabilities

Other current liabilities	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Other current liabilities	Other current liabilities Other current liabilities are comprised of the following: (In US$ millions) December 31, 2017 December 31, 2016 Taxes payable 70 148 Deferred mobilization revenue 37 107 Intangible liabilities - unfavorable contracts (1) 23 43 Employee withheld taxes, social security and vacation payments 15 55 Accrued interest expense 3 69 Construction obligation (2) — 500 Derivative financial instruments (3) — 236 Accrued expenses 103 116 Other current liabilities 17 78 Total other current liabilities (4) 268 1,352 (1) Intangible liabilities represent the estimated fair values of acquired unfavorable drilling contracts. Refer to Note 20 "Goodwill and other intangible assets and liabilities" for more information. (2) A construction obligation was recognized upon the acquisition of Sevan Drilling for the Sevan Developer . On April 27, 2017 the construction obligation increased to $526 million following refunds received from Cosco, taking the delivery installment back to the contract price. In July 2017, Sevan and Cosco agreed to further defer the Sevan Developer delivery until June 30, 2020. The contract amendment included a contract termination clause for Cosco and, as Sevan does not have termination rights, it was deemed to have lost control of the asset and therefore derecognized both the newbuild asset, construction obligation and accrued interest. Refer to Note 6 "(Loss)/gain on disposals" for more information. (3) On filing for Chapter 11, an event of default under each of our derivative agreements was triggered, resulting in the termination of the derivative financial instruments on September 13, 2017. As a result, the outstanding derivative balance was held at the counterparty claimed value within "Liabilities subject to compromise" on the Consolidated Balance Sheet as at December 31, 2017 . Refer to Note 31 "Risk management and financial instruments" for more information. (4) Balances held as at December 31, 2017 exclude liabilities that are subject to compromise, which have been reclassified to a separate line within the Consolidated Balance Sheet. This represents our estimate of known or potential pre-petition claims to be resolved in connection with the Chapter 11 proceedings. Refer to Note 1 "General Information".

Other non-current liabilities

Other non-current liabilities	12 Months Ended
	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Other non-current liabilities	Other non-current liabilities Other non-current liabilities are comprised of the following: (In US$ millions) December 31, 2017 December 31, 2016 Accrued pension liabilities 6 3 Deferred mobilization revenues 18 55 Intangible liabilities - unfavorable contracts (1) — 23 Other non-current liabilities 43 38 Total other non-current liabilities (2) 67 119 (1) Intangible liabilities represent the estimated fair values of acquired unfavorable drilling contracts. Refer to Note 20 - "Goodwill and other intangible assets and liabilities" for more information. (2) Balances held as at December 31, 2017 exclude liabilities that are subject to compromise, which have been reclassified to a separate line within the Consolidated Balance Sheet. This represents our estimate of known or potential pre-petition claims to be resolved in connection with the Chapter 11 proceedings. Refer to Note 1 "General Information".

Common shares

Common shares	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Common shares	Common shares December 31, 2017 December 31, 2016 December 31, 2015 All shares are common shares of $2.00 par value each Shares US$ millions Shares US$ millions Shares US$ millions Authorized share capital 800,000,000 1,600 800,000,000 1,600 800,000,000 1,600 Issued and fully paid share capital 508,763,020 1,017 508,763,020 1,017 493,078,680 986 Treasury shares held by the Company (4,244,080 ) (9 ) (4,318,740 ) (9 ) (318,740 ) (1 ) Outstanding shares in issue 504,518,940 1,008 504,444,280 1,008 492,759,940 985 As at December 31, 2017 , our shares were listed on the Oslo Stock Exchange and the New York Stock Exchange. We were incorporated on May 10, 2005 and 6,000 ordinary shares of par value $2.00 each were issued. Since incorporation the number of issued shares has increased from 6,000 to 508,763,020 of par value $2.00 each as at December 31, 2017 . There were 15,684,340 new shares issued in 2016 due to the conversion of convertible bonds, refer to Note 22 "Long-term debt" for further information. In 2015 there were no new shares issued. A share repurchase program was approved by the Board in 2007 giving us the authorization to buy back shares. Shares bought back under the authorization may be cancelled or held as treasury shares. Treasury shares may be held to meet our obligations relating to the share option plans. As at December 31, 2017 we held 4,244,080 treasury shares and net shares outstanding at December 31, 2017 were 504,518,940 . In November 2014 , the Board authorized a share buyback program under which we may repurchase up to approximately 10% of shares outstanding. We may repurchase shares from time to time in open market transactions or private transactions in accordance with applicable securities laws. The timing and amount of any repurchases will be determined by management, based on their evaluation of market conditions, capital allocation opportunities, and other factors. The program does not require us to repurchase any specific number of shares and may be modified, suspended, extended or terminated by us at any time without prior notice. In May 2015 , however, as part of the amendments to the covenants contained in our senior secured credit facilities, we are restricted from buying back any shares during the amendment period until January 1, 2017 . In addition, in April 2016, as part of the amendments to the covenants contained in our senior secured credit facilities, we are restricted from making dividend distributions during the amendment period until June 30, 2017. In April 2017, the restricted period was amended to September 30, 2017. During the year ended December 31, 2016 , as a result of the share-for-debt exchange the number of our common shares outstanding increased by 15,684,340 shares. Refer to Note 22 "Long-term debt" for additional information. On September 5, 2016 we repurchased 4,000,000 shares in settlement of our total return swap agreements. This was completed at a strike price of NOK20.3 . Refer to Note 31 "Risk management and financial instruments" for further information. As of the Chapter 11 Filing Date, September 12, 2017, we had 508,763,020 common shares outstanding. We will continue to account for our common shares at their carrying value until a plan confirmed by the Bankruptcy Court becomes effective, which may result in an adjustment. Equity offerings and drilling unit sale transactions with Seadrill Partners The following table summarizes the issuances of common units for Seadrill Partners between their IPO in October 2012 until the deconsolidation of Seadrill Partners on January 2, 2014: Date Number of Common Units issued to the public Number of Common Units issued to Seadrill Offering price ($) Gross proceeds from public Net proceeds from public ($'millions) Seadrill's ownership after the offering October 24, 2012 (IPO) 10,062,500 14,752,525 22.00 221 203 75.67 % October 18, 2013 — 3,310,622 32.29 — — 77.47 % December 13, 2013 12,880,000 3,394,916 29.50 380 365 62.35 % The following table summarizes the sale of our drilling units to Seadrill Partners between its IPO until the deconsolidation of Seadrill Partners on January 2, 2014: (In US$millions) T-15 T-16 West Sirius West Leo Total Adjusted sales price * 74 68 922 729 1,793 Less net assets transferred 5 — (375 ) (116 ) (486 ) Excess of sales price over net assets transferred 79 68 547 613 1,307 Deemed contribution to Seadrill shareholders from non-controlling interest 19 16 105 69 209 * The adjusted sales price above includes debt assumed and working capital adjustments. These transactions were deemed to be reorganizations of entities under common control and accordingly no gains or losses were recognized by us. On May 17, 2013, we sold its 100% interest in the entities that own and operate the tender rig T-15 to Seadrill Partners a total purchase price of $210 million , less approximately $101 million of debt outstanding, less $35 million of working capital adjustments. The acquisition was funded by issuance of vendor financing loan to Seadrill Partners of $110 million . On October 18, 2013, we sold its 100% interest in the entity that owns the tender rig T-16 , and the beneficial interest in the T-16 drilling contract (collectively, the “T-16 Business”), to Seadrill Partners for a total purchase price of $200 million , less approximately $93 million of debt outstanding, less $39 million of working capital adjustments. As part of the consideration, Seadrill Partners issued 3,310,622 common units to Seadrill as consideration for the purchase in a private placement transaction at a price of $32.29 per unit. This resulted in an increase in net assets attributable to the non-controlling interest of $19 million . On December 13, 2013, we sold to Seadrill Partners: (i) 51% of its interest in each of the entities that own, operate and manage the semi-submersible drilling rig, West Sirius (the “ Sirius Business”); and (ii) 30% of its interest interests in each of the entities that own and operate the semi-submersible drilling rig, West Leo (the “Leo Business”). The implied purchase prices of the Sirius Business was $1,035 million , less debt assumed of $220 million , plus working capital adjustments of $107 million . The implied purchase prices of the Leo Business was $1,250 million , less debt assumed of $486 million , less working capital adjustments of $35 million . In relation to these acquisitions, Seadrill Partners issued 12,880,000 common units to the public (including 1,680,000 common units issued to underwriters) and 3,394,916 common units to Seadrill, at a price of $29.50 per unit. The gross proceeds raised from the public was $380 million , and the net proceeds raised after issuance fees was $365 million , of which $137 million was attributable to the non-controlling interest. This resulted in an increase in net assets attributable to the non-controlling interest of $83 million .

Non-controlling interest

Non-controlling interest	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Non-controlling interest	Non-controlling interest Our Consolidated Statement of Operations, Balance Sheet and Statement of Cash Flows include the results of NADL, Asia Offshore Drilling Ltd (“AOD”) and Sevan Drilling ASA (“Sevan”) for the year ended, and as at December 31, 2017 . We also consolidates certain variable interest entities relating to Ship Finance International. As at December 31, 2017 , we had the following ownership interests in these companies: 70.36% of NADL, 66.24% of Asia Offshore Drilling Ltd and 50.11% of Sevan Drilling ASA. The amount of shareholders’ equity not attributable to us is included in non-controlling interests. NADL In January 2014 , NADL completed its IPO in the United States of 13,513,514 common shares at $9.25 per share. The non-controlling interest recognized on the IPO was $52 million . Following NADL’s 1 for 10 reverse stock split as at December 31, 2015 , there were no changes in the percentage of NADL owned by the non-controlling interest. AOD On March 25, 2013 , we obtained control of the Board of Asia Offshore Drilling Ltd and owned 66.18% of the outstanding shares. As a result of obtaining control, we have consolidated the results and financial position of Asia Offshore Drilling Ltd from this date. The fair value of the non-controlling interest established upon obtaining a controlling financial interest was $100 million . Subsequent to the date of consolidation, our percentage ownership increased to 66.21% , and then increased again to 66.24% . Ship Finance VIEs In 2007 and 2008 we entered into sale and leaseback arrangements for drilling units with Ship Finance International Ltd, who incorporated subsidiary companies for the sole purpose of owning and leasing the drilling units. We had recognized these subsidiary companies as VIEs and concluded that we are their primary beneficiary. Accordingly, these subsidiary companies are included in our Consolidated Financial Statements, with the Ship Finance International Ltd equity in these companies included in non-controlling interest. In 2012 , we acquired all the shares in one of these Ship Finance International Ltd companies, Rig Finance II Ltd for $47 million . As a consequence of this, Rig Finance II Ltd is no longer treated as a VIE but a wholly owned subsidiary. In 2013 these VIEs declared dividends of $223 million to Ship Finance International Limited. In December 2014 , we acquired all the shares of the Ship Finance International Ltd company, SFL Polaris Ltd, for a consideration of $111 million . The non-controlling interest derecognized was $7 million . As a consequence of this, SFL Polaris Ltd is no longer treated as a VIE but a wholly owned subsidiary. Refer to Note 34 "Variable interest entities" for more information. During the period ended December 31, 2017 $14 million of dividends were declared by VIEs to Ship Finance and was settled against related party balances with Ship Finance ( December 31, 2016 : $113 million ). Seadrill Partners On October 24, 2012 , Seadrill Partners completed its IPO of 10,062,500 common units representing limited liability company interests in Seadrill Partners at a price of $22.00 per unit, for gross proceeds of $221 million and net proceeds after issuance costs of $203 million (including 1,312,500 common units issued in connection with the exercise of the over-allotment option). Seadrill Partners is listed on the New York stock exchange under the symbol “SDLP.” Upon completion of the offering, we owned 14,752,525 common units and 16,543,350 subordinated units which represents 75.67% of the limited liability company interests in Seadrill Partners. Subsequent to the IPO, in October 2013 , Seadrill Partners issued 3,310,622 common units to us, which increased our total ownership interest to 77.47% . In December 2013 , Seadrill Partners issued a further 3,394,916 common units to us and 12,880,000 common units to the public, which had the effect of reducing our ownership total ownership to 62.35% . The effect of these transactions was to increase the non-controlling interest by $239 million . During the period from Seadrill Partners’ IPO in October 2012 until the time of its first effective Annual General Meeting (“AGM”) on January 2, 2014 , we retained the sole power to appoint, remove and replace all members of Seadrill Partner’s board of directors. From the first AGM, the majority of the board members became electable by the common unitholders and accordingly, from this date we no longer retained the power to control the Board of Directors as a result of certain provisions in the Operating Agreement which limits our ability to vote our full holding of common units in an election of Directors to the Board of Seadrill Partners. As at January 2, 2014 , Seadrill Partners was considered to be an associated company and not a controlled subsidiary of ours, and as such Seadrill Partners was deconsolidated by us. The non-controlling interest derecognized was $115 million . Refer to Note 11 "Disposal of businesses and deconsolidation of subsidiaries" for more information. Purchase of 10% interest in Seadrill Mobile Units Nigeria Limited On December 5, 2016 , our wholly owned subsidiary Seadrill UK Ltd. acquired a 10% interest that an unrelated party, HH Global Alliance Investments Limited (“HHL”) held in Seadrill Mobile Units (Nigeria) Ltd, the service company for West Capella, for a fair value of $6.6 million . Following the completion of this transaction Seadrill UK Ltd. owns 49% of Seadrill Mobile Units Nigeria Limited, with the remaining 51% being owned by subsidiaries of Seadrill Partners. Simultaneously HHL acquired from Seadrill UK Ltd. a 49% interest in Seadrill Nigeria Operations Limited, the service company for West Jupiter for a fair value of $6.6 million . The impact of these transactions was to increase Seadrill’s direct ownership interest in Seadrill Partners by $6.6 million , and to recognize HHL’s non-controlling interest in Seadrill Nigeria Operations Ltd of $6.6 million . During the year ended December 31, 2017 , HHL acquired a further 2% interest in Seadrill Nigeria Operations Ltd for total consideration of $0.3 million . Changes in non-controlling interest for the years ended December 31, 2017 , 2016 and 2015 are as follows: (In US$ millions) Ship Finance International Ltd VIEs North Atlantic Drilling Ltd Asia Offshore Drilling Ltd Sevan Drilling ASA Seadrill Nigeria Operations Limited Total December 31, 2014 32 205 134 251 4 626 Changes in 2015 — 8 (14 ) — (4 ) (10 ) Net income attributable to non-controlling interest in 2015 30 (16 ) 20 59 — 93 Impairment of goodwill (48 ) — (18 ) — — — (28 ) — — (94 ) December 31, 2015 14 179 140 282 — 615 Changes in 2016 (112 ) 7 — — 6 (99 ) Net income attributable to non-controlling interest in 2016 29 (21 ) 9 9 — 26 December 31, 2016 (69 ) 165 149 291 6 542 Changes in 2017 (14 ) — — — — (14 ) Net income attributable to non-controlling interest in 2017 24 (89 ) — (65 ) 1 (129 ) December 31, 2017 (59 ) 76 149 226 7 399

Accumulated other comprehensive

Accumulated other comprehensive income/(loss)	12 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income/(loss)	Accumulated other comprehensive income/(loss) Accumulated other comprehensive income consists of the following: (In US$ millions) Unrealized gain on marketable securities Unrealized gain on foreign exchange Actuarial gain/(loss) relating to pension Share in unrealized gains from associated companies Other Total Balance as at December 31, 2016 17 36 (23 ) 23 — 53 Other comprehensive income before reclassifications 14 — (3 ) 2 2 15 Amounts reclassified from accumulated other comprehensive income — — — (10 ) — (10 ) Balance as at December 31, 2017 31 36 (26 ) 15 2 58 The unrealized gain on marketable securities relates to the accumulated gains on the investment in Seadrill Partners Common Units and the recognition and subsequent remeasurement of our investment in Archer. Refer to Note 13 "Marketable securities" for more information. The applicable amount of income taxes associated with each component of other comprehensive income is nil , other than on the actuarial loss on pension, due to the fact that the items relate to companies domiciled in non-taxable jurisdictions. For actuarial loss related to pension, the accumulated applicable amount of income taxes is $1 million ( $1 million in 2016 ) as this item is related to companies domiciled in Norway where the tax rate is 24% ( 2016 : 24% ).

Share based compensation

Share based compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share based compensation	Share based compensation The share based compensation expense for our share option and Restricted Stock Unit ("RSU") plans recognized in the Consolidated Statement of Operations for the year ended December 31, 2017 was $7 million ( 2016 : $7 million , 2015 : $7 million ). The grant-date fair value of employee share options and similar instruments is estimated using the Black-Scholes option-pricing model. The grant date fair value of the RSU is determined as the market trading price on that date. The fair value of the awards expected to vest is recognized as compensation cost straight-line over the vesting period. As at December 31, 2017 there was a total of $9 million in unrecognized compensation costs related to non-vested Company's Options and RSU plans which is expected to be recognized over weighted average period of 1 year . Share Options Our shareholders have authorized the Board to establish and maintain Option Schemes in order to encourage our directors, officers and other employees to hold shares in our Company. The Option Scheme for U.S. employees expired in March 2018 , whereas the Option Scheme for international employees will expire in May 2020 . On February 16, 2017, the Board approved a new Share Option Scheme that will expire in February 2027. The Option Schemes permit the Board, at its discretion, to grant options to the employees and directors of our company or our subsidiaries to acquire our shares. The options are not transferable. The subscription price is at the discretion of the Board, provided the subscription price is never reduced below the par value of the share. The subscription price for certain options granted under the Option Schemes will be reduced by the amount of all dividends declared by us in the period from the date of grant until the date the option is exercised. Options granted under the Option Schemes will vest at a date determined by the board at the date of the grant. The options granted under the plan to date vest over a period of one to five years . There is no maximum number of shares authorized for awards of equity share options and authorized, unissued or treasury shares of ours may be used to satisfy exercised options. The following table summarizes share option transactions related to the Seadrill Scheme in 2017 , 2016 and 2015 : December 31, 2017 December 31, 2016 December 31, 2015 Options Weighted average exercise price $ Options Weighted average exercise price $ Options Weighted average exercise price $ Outstanding at beginning of year 947,500 20.08 2,015,171 28.53 2,241,116 35.10 Granted — — — — 710,000 12.04 Exercised — — — — — — Forfeited (410,000 ) 22.06 (1,067,671 ) 35.29 (935,945 ) 32.81 Outstanding at end of year 537,500 11.62 947,500 20.08 2,015,171 28.53 Exercisable at end of year 358,959 11.65 412,917 25.79 882,152 36.14 Options granted in November 2010 had exercise prices of NOK 192.90 ( $31.40 ) for American citizens or residents and NOK 185.20 ( $31.06 ) for non-Americans. They were exercisable one fifth each year beginning 12 months after they were granted and expired in December 2015 . Options granted in November 2011 had exercise prices of NOK 202.10 ( $34.68 ) and can be exercised one fourth at a time, after the first 18 , 36 , 48 and 60 months from the grant date. They expired in December 2016 . Options granted during 2012 had exercise prices, ranging from NOK 205.30 to NOK 224.53 . They have the same exercise schedule as the 2011’s grants and expired between September 2015 and December 2017 . The weighted average fair value of the options granted in 2012 was $10.23 . Options granted in October 2013 had an exercise prices ranging from NOK249 to NOK273 and can be exercised one fourth at a time after 13 , 25 , 37 and 49 months from the grant date. The weighted average fair value of the options granted in October 2013 was $10.23 . Options granted in December 2015 had an exercise price of NOK93.70 and can be exercised one third at a time after 12, 24 and 36 months . They expire in May 2020 . The weighted average fair value of the options granted in December 2015 was $3.33 . The grant-date fair value of employee share options is estimated using the Black-Scholes option-pricing model with the following assumptions used in estimating fair value for grants issued 2015: 1.6% risk-free interest rate, volatility of 34.8% , 0% dividend yield and an expected option term of three years, six months. The risk-free interest rates were estimated using the US Treasury yield curve in effect at the time of grant for instruments with a similar life. The dividend yield has been estimated at 0% as the exercise price is reduced by all dividends declared by us from the date of grant to the exercise date. It is also assumed that 100% of options granted will vest. There were 537,500 options outstanding at December 31, 2017 ( 2016 : 947,500 ). Their weighted average remaining contractual life was 9 months ( 2016 : 34 months ). During 2017 the total intrinsic value of options exercised was nil ( 2016 : nil , 2015 : nil ) on the day of exercise. The intrinsic value of options fully vested but not exercised at December 31, 2017 was zero since the weighted average exercise price per share exceeded the market price of our shares as at that date. Restricted Stock Units Under the terms of the RSU plans, the holder of an award is entitled to receive a share in us if they are still employed at the end of the three year vesting period. There is no requirement for the holder to pay for the share on the grant date or upon the vesting of the award. In addition, the holders are entitled to receive an amount equal to the ordinary dividends declared and paid on our shares during the vesting period. Seadrill Restricted Stock Units The following table summarizes the RSU activity for us for the years ended December 31, 2017 , 2016 and 2015 : Restricted Stock Units - Seadrill December 31, 2017 December 31, 2016 December 31, 2015 Outstanding at beginning of year 5,186,724 1,402,980 525,210 Granted — 4,349,158 937,970 Exercised (74,660 ) (249,050 ) — Forfeited (798,127 ) (316,364 ) (60,200 ) Outstanding at end of year 4,313,937 5,186,724 1,402,980 On October 1, 2013 , the Board of the Company approved 373,700 awards under our Restricted Stock Units “RSU” plan. The fair value on the date of grant was $46.07 . These awards were settled in December 2016 . In December 2014 , the Board of the Company approved 162,560 awards under our RSU plan. The fair value on the date of grant was $11.00 . In May 2015 , the Board of the Company granted 28,000 awards under our RSU plan. In December 2015 , the Board of the Company approved further 909,970 awards under our RSU plan. The fair value on the date of grant was $11.91 and $3.67 , respectively. In April 2016 , the Board of the Company granted 2,066,658 awards under our RSU plan. In December 2016 , the Board of the Company granted additional 2,282,500 awards under the RSU's plan. The fair value on the date of grant was $3.82 and $3.81 , respectively. The RSA contemplates certain changes to equity-based employee incentive plans at closing. The transactions contemplated by the RSA are subject to court approval and other terms and conditions. NADL Restricted Stock Units The following table summarizes the RSU activity for NADL for the years ended December 31, 2017 , 2016 and 2015 : Restricted Stock Units - NADL December 31, 2017 December 31, 2016 December 31, 2015 Outstanding at beginning of year 413,702 174,583 253,870 Granted — 270,653 1,587,719 Settled — (20,837 ) — Adjustment (1) — — (1,571,251 ) Forfeited (300 ) (10,697 ) (95,755 ) Outstanding at end of year 413,402 413,702 174,583 (1) Adjustment relates to NADL's reverse stock split in December 2015 , as discussed above. On November 7, 2013 , the Board of the Company's consolidated subsidiary, NADL, approved 278,778 awards under NADL`s RSU plan with a fair value based on the market share price on grant date of $96.50 . These awards were settled in December 2016 . In January 2015 , the Board of NADL granted 109,219 awards and in December 2015 , an additional 1,478,500 awards under NADL's RSU plan. The fair value on the date of grant was $14.10 and $3.70 , respectively. In December 2015 the shareholders of NADL in a special general meeting approved a capital reorganization including a 1-for- 10 reverse stock split of our issued and outstanding common shares and reducing par value from $5.00 to $0.10 . As a result of the capital restructuring the number of RSUs has been adjusted by 1,571,250 units. In April 2016 , the Board of NADL granted 118,653 awards and in December 2016 , an additional 152,000 awards under the NADL's RSU plan. The fair value on the date of grant was $2.95 and $3.62 , respectively. Interests in the existing NADL common shares will be extinguished under the Plan. Holders of existing NADL common shares are expected to receive no recovery. The RSA contemplates certain changes to equity-based employee incentive plans at closing. The transactions contemplated by the RSA are subject to court approval and other terms and conditions.

Pension benefits

Pension benefits	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Pension benefits	Pension benefits Defined benefit plans NADL has several defined benefit pension plans covering substantially all Norwegian employees. All of the plans are administered by a life insurance company. For onshore employees in Norway, who are participants in the defined benefit plans, the primary benefits are a retirement pension of approximately 66 percent of salary at retirement age of 67 years, together with a long-term disability pension. The retirement pension per employee is capped at an annual payment of 66 percent of the total of 12 times the Norwegian Social Security Base. Most employees in this group may choose to retire at 62 years of age on a pre-retirement pension. Offshore employees in Norway have a retirement and long-term disability pension of approximately 60 percent of salary at retirement age of 67 . Most offshore employees on drilling units may choose to retire at 60 years of age on a pre-retirement pension. During the period ended December 31, 2016 , a number of employees left and as a result the defined benefit scheme transferred the pension liability for these employees to the life insurance company administering the scheme. In addition, one of the defined benefit schemes has closed down and the members transferred into a new defined contribution scheme. The difference between the reduction in benefit obligation and reduction in the plan assets transferred to the life insurance company has been recognized within "Total net pension cost". In addition, net unrecognized actuarial losses have been recognized as a result of the settlement within the "Total net pension cost". The net impact of the settlement was a gain of $1 million . Consolidated Balance Sheet position (In US$ millions) December 31, 2017 December 31, 2016 Accrued pension liabilities - Non-current liabilities 6 3 Less: Deferred tax (Asset) (2 ) (1 ) Shareholders equity 4 2 Annual pension cost Year ended December 31, (In US$ millions) 2017 2016 2015 Service cost 2 7 12 Interest cost on prior years’ benefit obligation 2 3 4 Gross pension cost for the year 4 10 16 Expected return on plan assets (1 ) (4 ) (3 ) Administration charges — — 1 Net pension cost for the year 3 6 14 Social security cost — 1 2 Amortization of actuarial gains/losses — 1 3 Impact of settlement/curtailment funded status (1 ) (1 ) — Total net pension cost 2 7 19 The funded status of the defined benefit plan (In US$ millions) December 31, 2017 December 31, 2016 Projected benefit obligations at end of period 38 60 Plan assets at market value (33 ) (58 ) Accrued pension liability exclusive social security 5 2 Social security related to pension obligations 1 1 Accrued pension liabilities 6 3 Change in projected benefit obligations (In US$ millions) December 31, 2017 December 31, 2016 Projected benefit obligations at beginning of period 60 130 Interest cost 2 3 Service cost 2 7 Benefits paid (2 ) (3 ) Change in unrecognized actuarial gain (3 ) (28 ) Settlement (24 ) (54 ) Foreign currency translations 3 5 Projected benefit obligations at end of period 38 60 Change in pension plan assets (In US$ millions) December 31, 2017 December 31, 2016 Fair value of plan assets at beginning of year 58 97 Estimated return 1 4 Contribution by employer 1 9 Administration charges — — Benefits paid (2 ) (3 ) Change in unrecognized actuarial loss (5 ) (1 ) Settlement (23 ) (52 ) Foreign currency translations 3 4 Fair value of plan assets at end of year 33 58 The accumulated benefit obligation for all defined benefit pension plans was $33 million and $54 million at December 31, 2017 and 2016 , respectively. Pension obligations are actuarially determined and are critically affected by the assumptions used, including the expected return on plan assets, discount rates, compensation increases and employee turnover rates. We periodically review the assumptions used, and adjust them and the recorded liabilities as necessary. During the year a number of employees left and as a result the defined benefit scheme transferred the pension liability for these employees to the life insurance company administering the scheme. The difference between the reduction in benefit obligation and the plan assets transferred to the life insurance company has been recognized within “Other comprehensive income.” The settlement is not deemed to be significant in the context of the overall scheme and as such net unrecognized actuarial losses have not been recycled as a result of the settlement. The expected rate of return on plan assets and the discount rate applied to projected benefits are particularly important factors in calculating our pension expense and liabilities. We evaluate assumptions regarding the estimated rate of return on plan assets based on historical experience and future expectations on investment returns, utilizing the asset allocation classes held by the plan’s portfolios. The discount rate is based on the covered bond rate in Norway. Changes in these and other assumptions used in the actuarial computations could impact the projected benefit obligations, pension liabilities, pension expense and other comprehensive income. Assumptions used in calculation of pension obligations Year ended December 31, 2017 2016 2015 Rate of compensation increase at the end of year 2.50 % 2.50 % 2.50 % Discount rate at the end of year 2.40 % 2.10 % 2.70 % Prescribed pension index factor 1.50 % 1.20 % 1.20 % Expected return on plan assets for the year 2.40 % 3.00 % 3.30 % Employee turnover 4.00 % 4.00 % 4.00 % Expected increases in Social Security Base 2.25 % 2.25 % 2.50 % The weighted-average asset allocation of funds related to our defined benefit plan at December 31, was as follows: Pension benefit plan assets December 31, 2017 December 31, 2016 Equity securities 10.6 % 7.1 % Debt securities 66.1 % 54.7 % Real estate 8.8 % 9.4 % Money market 13.5 % 28.1 % Other 1.0 % 0.7 % Total 100.0 % 100.0 % The investment policies and strategies for the pension benefit plan funds do not use target allocations for the individual asset categories. The investment objectives are to maximize returns subject to specific risk management policies. We diversify our allocation of plan assets by investing in both domestic and international fixed income securities and domestic and international equity securities. These investments are readily marketable and can be sold to fund benefit payment obligations as they become payable. Cash flows - Contributions expected to be paid The table below shows our expected annual pension plans contributions under defined benefit plans for the years ending December 31, 2018-2027 . The expected payments are based on the assumptions used to measure our obligations at December 31, 2017 and include estimated future employee services. (In US$ millions) December 31, 2017 2018 3 2019 3 2020 3 2021 3 2022 3 2023-2027 15 Total payments expected during the next 10 years 30 Defined contribution and other plans We made contributions to personal defined contribution pension and other plans totaling $17 million , $26 million and $29 million for the years to December 31, 2017 , 2016 and 2015 , respectively. These were charged to operations as they became payable.

Related party transactions

Related party transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related party transactions	Related party transactions The significant related parties of Seadrill are as follows: (i) Transactions with investees and associates, over which we have significant influence: • Seadrill Partners • SeaMex • Seabras Sapura (ii) Transactions with those holding significant influence over Seadrill: • Hemen and affiliated companies Seadrill Partners As at January 2, 2014 , the date of deconsolidation, Seadrill Partners is considered to be a related party and not a controlled subsidiary of Seadrill. Prior to the deconsolidation, Seadrill Partners was a consolidated subsidiary of Seadrill, and all inter-group transactions were eliminated in our Consolidated Financial Statements. The net income/(expense) with Seadrill Partners for the years ended December 31, 2017 , 2016 , and 2015 were as follows: Year ended December 31, (In US$ millions) 2017 2016 2015 Management fees charged to Seadrill Partners - Other revenues (a) and (b) 75 65 75 Rig operating expenses charged to Seadrill Partners - Other revenues (c) 23 25 29 Contingent consideration 27 21 47 Insurance premiums charged to Seadrill Partners (d) 11 16 20 Rig operating costs charged by Seadrill Partners (e) (5 ) (11 ) (13 ) Bareboat charter arrangements (f) 3 10 (2 ) Intercompany inventory purchases (2 ) (1 ) — Interest expenses charged to Seadrill Partners (g) 6 12 16 Interest recognized on deferred consideration receivable 5 5 8 Derivatives recharged to Seadrill Partners (h) 1 4 10 Net related party income from Seadrill Partners 144 146 190 Receivables/(payables) with Seadrill Partners and its subsidiaries as at December 31, 2017 and 2016 consisted of the following balances: (In US$ millions) December 31, December 31, Rig financing agreements and Loan Agreements (i) 25 160 $109.5 million Vendor financing loan (j) — — Deferred consideration receivable (k) 52 61 Other receivables (l) 157 189 Other payables (l) (24 ) (80 ) The following is a summary of the related party agreements with Seadrill Partners: a) Management and administrative service agreements Certain subsidiaries of Seadrill Partners are in a management and administrative services agreement with Seadrill Management, a wholly owned subsidiary of Seadrill, pursuant to which Seadrill Management provides to Seadrill Partners certain management and administrative services. The services provided by Seadrill Management are charged at cost plus management fee to be agreed upon from time to time by the parties. In April 2016, the agreement was extended for an indefinite term and can be terminated providing 90 days written notice. During the twelve months ended December 31, 2017, the management fee has ranged from 4.85% to 8% of costs and expenses incurred in connection with providing these services. b) Technical and administrative service agreement Certain subsidiaries of Seadrill Partners entered into advisory, technical and/or administrative services agreements with subsidiaries of Seadrill. The services provided by our subsidiaries are charged at cost plus service fee equal to approximately 5% of costs and expenses incurred in connection with providing these services. Income recognized under the above agreements (a) & (b) for the period ended December 31, 2017 was $75 million ( 2016 : $65 million ; 2015 : $75 million ). c) Rig operating costs charged to Seadrill Partners We have charged to Seadrill Partners certain rig operating costs in relation to costs incurred on behalf of the West Polaris operating in Angola in 2017, 2016 and 2015 and the West Vencedor which operated in Angola in 2015. The total other revenues earned for the year ending December 31, 2017 was $23 million ( 2016 : $25 million ; 2015 : $29 million ). d) Insurance premiums We negotiate insurance for drilling units on a centralized basis. The total insurance premiums related to Seadrill Partners drilling units recharged to Seadrill Partners were $10.5 million for the year ending December 31, 2017 ( 2016 : $16 million ; 2015 : $20 million ). e) Rig operating costs charged by Seadrill Partners Seadrill Partners has charged to Seadrill, through its Nigerian service company, certain services, including the provision of onshore and offshore personnel, which was provided for the West Jupiter and West Saturn drilling rigs operating in Nigeria. The total rig operating expenses incurred for the period ending December 31, 2017 was $5 million ( 2016 : $11 million ; 2015 : $13 million ). f) Bareboat charter arrangements In connection with the transfer of the West Aquarius operations to Canada, the West Aquarius drilling contract was assigned to Seadrill Canada Ltd., a wholly owned subsidiary of Seadrill Partners, necessitating certain changes to the related party contractual arrangements relating to the West Aquarius . Seadrill China Operations Ltd, the owner of the West Aquarius and a wholly-owned subsidiary of Seadrill Partners, had previously entered into a bareboat charter arrangement with Seadrill Offshore AS, a wholly-owned subsidiary of Seadrill, providing Seadrill Offshore AS with the right to use the West Aquarius . In October 2012, this bareboat charter arrangement was replaced with a new bareboat charter between Seadrill China Operations Ltd and Seadrill Offshore AS, and at the same time, Seadrill Offshore AS entered into a bareboat charter arrangement providing Seadrill Canada Ltd. with the right to use the West Aquarius in order to perform its obligations under the drilling contract described above. For year ended December 31, 2017 the net effect to Seadrill of the bareboat charters was an expense of $3 million ( 2016 : $10 million , 2015 : $2 million ).The contract was terminated effective April 19, 2017 on completion of the rig's contract with Hibernia Management. (g) Interest expenses and loss on derivatives The total interest charged to Seadrill Partners for the loan arrangements, including commitment fees and other fees, was $6 million for the period ending December 31, 2017 ( 2016 : $12 million ; 2015 : $16 million ). Refer to the sections below for details on the financing arrangements. (h) Derivative interest rate swap agreements We previously held interest rate swap agreements with Seadrill Partners on a back to back basis with certain of our own interest rate swap agreements. On commencement of Chapter 11 proceedings the derivative position held by Seadrill was cancelled and held at the claimed value by the derivative counterparty. This resulted in no further recharged gains or losses on derivatives after September 12, 2017. The total net derivative gains and losses charged to Seadrill Partners for the year ended December 31, 2017 was $1 million , ( 2016 : $1 million ; 2015 : $10 million ). (i) Rig Financing Agreements West Vencedor Facility - In June 2014 we repaid the underlying $1,200 million senior secured loan relating to the West Vencedor , and as a result the West Vencedor Loan Agreement between us and Seadrill Partners was amended to carry on the existing loan on the same terms. The West Vencedor Loan Agreement between us and Seadrill Partners was scheduled to mature in June 2015 and all outstanding amounts thereunder would be due and payable, including a balloon payment of $70 million . On April 14, 2015 the Loan Agreement was amended and the maturity date was extended to June 25, 2018 . The West Vencedor Loan Agreement bears a margin of 2.25% , a guarantee fee of 1.4% and a balloon payment of $21 million due at maturity in June 2018 . The total amount owed by Seadrill Partners to Seadrill under the remaining West Vencedor Loan agreement as at December 31, 2017 was $25 million ( December 31, 2016 : $41 million ). T-15 / T-16 Facility - The total amounts owed under the Rig Financing Agreement relating to the T-15 and T-16 were amended in August 2017 so that the facility is held in Seadrill Partners therefore removing the back to back agreement with Seadrill. As a result, the total amount outstanding at at December 31, 2017 was nil ( December 31, 2016 : $119 million ). West Vela facility - Under the terms of the $1,450 million secured credit facility agreement, certain subsidiaries of Seadrill and Seadrill Partners relating to the West Vela and West Tellus , were jointly and severally liable for their own debt and obligations under the facility and the debt and obligations of other borrowers who are also party to such agreement. In August 2017, Seadrill Partners completed amendments to the facility to insulate itself from events of default related to our potential use of Chapter 11 proceedings to implement our restructuring plan. The amendments remove Seadrill as a guarantor for this facility. West Polaris facility - In June 2015 , we completed the sale of the entities that own and operate the West Polaris to Seadrill Partners. One of the entities sold was the sole borrower under $420 million senior secured credit facility. Refer to Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information. Prior to August 2017, we acted as a guarantor under the facility. In August 2017, Seadrill Partners completed amendments to the facility to insulate itself from events of default related to our potential use of Chapter 11 proceedings to implement our restructuring plan. The amendments remove Seadrill as a guarantor for this facility. (j) $109.5 million Vendor financing loan In May 2013 , Seadrill Partners borrowed $109.5 million from Seadrill as vendor financing to fund the acquisition of the T-15 . The loan bore interest at a rate of LIBOR plus a margin of 5% and matured in May 2016 . (k) Deferred consideration receivable On the disposal of the West Vela and West Polaris to Seadrill Partners, we recognized deferred consideration receivables. Refer to the sections below for more information. West Polaris Disposal On June 19, 2015 , we sold the entities that owned and operated the West Polaris (the “Polaris business”), to Seadrill Operating LP (“Seadrill Operating”), a consolidated subsidiary of Seadrill Partners LLC and 42% owned by us. The entities continue to be related parties subsequent to the sale. In August 2017, Seadrill Partners completed amendments to the facility to insulate itself from events of default related to our potential use of Chapter 11 proceedings to implement our restructuring plan. The amendments remove Seadrill as a guarantor for this facility. Refer to Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information. (l) Receivables and Payables Receivables and payables with Seadrill Partners and its subsidiaries are comprised of management fees, advisory and administrative services, and other items including accrued interest. In addition, certain receivables and payables arise when we pay an invoice on behalf of Seadrill Partners or its subsidiaries and vice versa. Receivables and payables are generally settled quarterly in arrears. Trading balances to Seadrill Partners and its subsidiaries are unsecured and are intended to be settled in the ordinary course of business. West Sirius bareboat charter financing loan In December 2015 , an operating subsidiary of Seadrill Partners borrowed from a subsidiary of Seadrill $143 million in order to provide sufficient immediate liquidity to meet the terms of its bareboat charter termination payment in connection with the West Sirius contract termination. The loan bears interest at a rate of LIBOR plus 0.56% and matured in July 2017 . The loan was repaid in full during the year ended December 31, 2017 ( December 31, 2016 outstanding balance: $39 million ). Concurrently, Seadrill borrowed $143 million from a rig owning subsidiary of Seadrill Partners in order to restore its liquidity with respect to the West Sirius bareboat charter financing loan referred to above. The loan bears interest at a rate of LIBOR plus 0.56% and matures in July 2017 . The loan was repaid in full during the year ended December 31, 2017 ( December 31, 2016 : $39 million ). Each of the loan parties understand and agree that the loan agreements act in parallel with each other. These transactions have been classified within current and non-current portions of "Amount due from related parties", "Amounts due to related parties" and "Long-term debt due to related parties". West Sirius Spare parts agreement During the year ended December 31, 2015 , a subsidiary of Seadrill entered into an agreement with Seadrill Partners to store spare parts of Seadrill Partners’ West Sirius rig while it is stacked. We are responsible at our own cost for the moving and storing of the spare parts during the stacking period. We may use the spare parts of the West Sirius during the stacking period, but must replace them as required by Seadrill Partners at its own cost. Guarantees Seadrill provides certain guarantees on behalf of Seadrill Partners. • Guarantees in favor of customers, which guarantee the performance of the Seadrill Partners drilling units, totaled $165 million as at December 31, 2017 ( 2016 : $185 million ); • Guarantees in favor of banks provided on behalf of Seadrill Partners totaled nil as at December 31, 2017 after Seadrill Partners insulated itself from us in August 2017 ( 2016 : $621 million ); and • Guarantees in favor of suppliers provided on behalf of Seadrill Partners, relating to custom guarantees in Nigeria, totaled $0.6 million ( 2016 : $0.4 million ). Related parties to Hemen Holding Limited (“Hemen”) Since our formation, Seadrill's largest shareholder has been Hemen, which currently holds approximately 23.6% of shares in us. We transact business with the following related parties, being companies in which Hemen has a significant interest: • Ship Finance International Limited (“Ship Finance”); • Metrogas Holdings Inc (“Metrogas”); • Archer; • Frontline Management (Bermuda) Limited (“Frontline”); and • Seatankers Management Norway AS (“Seatankers”). Ship Finance Transactions We have entered into sale and lease back contracts for several drilling units, with subsidiaries of Ship Finance. We have determined that the Ship Finance subsidiaries, which own the units, are variable interest entities (VIEs), and that we are the primary beneficiary of the risks and rewards connected with the ownership of the units and the charter contracts. Accordingly, these VIEs are fully consolidated in our Consolidated Financial Statements. The equity attributable to Ship Finance in the VIEs is included in non-controlling interests in our Consolidated Financial Statements (Refer to Note 34 "Variable interest entities" to the Consolidated Financial Statements included herein for more information). The units that are currently leased back from Ship Finance are the West Taurus , West Hercules , and West Linus . The West Polaris was previously leased back from Ship Finance, but was repurchased in 2014, before subsequently being sold to Seadrill Partners, as described below. During the years ended December 31, 2017 , 2016 and 2015 , we incurred the following lease costs on units leased from the Ship Finance subsidiaries. Year ended December 31, (US$ millions) 2017 2016 2015 West Hercules 56 57 55 West Taurus 51 52 57 West Linus 83 82 81 Total 190 191 193 These lease costs are eliminated on consolidation. On June 28, 2013 , Seadrill's subsidiary NADL sold the entity that owns the newbuild jack-up, West Linus , to the Ship Finance subsidiary SFL Linus Ltd. The purchase consideration for this reflected the market value of the rig as at the delivery date which was $600 million . This rig was simultaneously chartered back over a period of 15 years to NADL. Upon closing, SFL Linus Ltd received a $195 million loan from Ship Finance which bears an interest of 4.5% per annum and matures in 2029 . During 2014 the loan was reduced to $125 million , and is reported as long-term debt due to related parties in our Consolidated Balance Sheet as at December 31, 2017 . As at December 31, 2017 the VIEs had gross and net loans outstanding to Ship Finance amounting $314 million , following a loan principal prepayment of $101m . As at December 31, 2016 the VIEs had gross loans of $415 million and net loans of $330 million due to the fact that the right of offset is established in the long-term loan agreements, and the balances are intended to be settled on a net basis. The net related party loans are disclosed as “Long-term debt due to related parties” on the Consolidated Balance Sheet. The loans bear interest at a fixed rate of 4.5% per annum. The total interest expense of the loans for 2017 was $15 million ( 2016 : $19 million , 2015 : $19 million ). Frontline Management transactions Frontline provides company secretarial support and administrative services for Seadrill, and charged us $3 million , $3 million and $4 million for these services in the years 2017 , 2016 and 2015 , respectively. These amounts are included in “General and administrative expenses”. Seatankers Management transactions We and our subsidiaries receive services from Seatankers Management Norway AS, an affiliate of Hemen. The fee was $2 million , $2 million , and $1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Other related parties Archer transactions From time to time, we may enter into transactions with Archer, Seadrill's former consolidated subsidiary and current associate investment, related to Archer’s working capital requirements and debt restructuring. Seadrill has provided a range of support for Archer including loans, guarantees and capital injections, in order to support the best interests of Archer and Seadrill. We have had the following transactions with Archer for the years ended December 31, 2017 , 2016 , and 2015 : Loan agreements On March 6, 2015 , we purchased a $50 million subordinated loan made by Metrogas, a related party, to Archer. The aggregate consideration paid for the loan by Seadrill to Metrogas was $51 million which is equal to the sum of the outstanding principal amount of $50 million and $1 million accrued commitment fee and interest on the loan. The loan bears interest at 7.5% per annum and has a commitment fee of 1% on any undrawn amount. As at the date of the purchase by us there was no undrawn amount. Interest and any commitment fee is due upon maturity of the loan on June 30, 2018 . In the year ended December 31, 2015 , our $50 million subordinated loan to Archer was written down to nil due to our share of net losses of Archer reducing the investment balance. Our accounting policy, once our investment in the common stock of an investee has reached nil, is to apply the equity method to other investments in the investees securities, loans and or advances based on seniority and liquidity. Our share of equity method losses or gains is determined based on the change in our claim on net assets of the investee. Archer’s net losses and other comprehensive income were therefore applied to our loan to Archer at our invested ownership of 39.89% . On May 27, 2016 , we granted a $75 million subordinated loan to Archer. The loan bears interest at a rate of 10.0% per annum and is repayable together with the interest on June 30, 2018 . Between May 27, 2016 and April 25, 2017, the $75 million loan was written down by $58 million due to our share of net losses of Archer reducing the investment balance. Our accounting policy, once the investment in the common stock of an investee has reached nil is to apply the equity method to other investments in the investees securities, loans and or advances based on seniority and liquidity. Our share and equity method losses or gains is determined based on the change in our claim on net assets of the investee. Archer’s net losses and other comprehensive income were therefore applied to our loan to Archer at our invested ownership of 39.72% for 2016 and an average position of 31.89% to April 25, 2017. On April 25, 2017, we agreed with Archer to convert the total outstanding subordinated loans, fees and interest provided to Archer, carrying value of $37 million , into a $45 million subordinated convertible loan. The subordinated convertible loan will bear interest of 5.5% , matures in December 2021 and has an option to convert into equity of Archer Limited in 2021 based on a strike price of $2.083 per share. The strike price is approximately 75% above the subscription price in Archer's private placement on March 2, 2017. As the new instrument is a convertible debt instrument, the instrument is bifurcated and subsequently recognized at fair value. For further information on the convertible option embedded derivative, please see Note 31 "Risk management and financial instruments". The total net interest income on the $50 million and $75 million loans relating to Archer for 2017 was $3.0 million ( 2016 : $8.0 million ; 2015 : $3.0 million ). The convertible debt instrument made a fair value gain on straight debt component of $1 million and a fair value loss on conversion option of $4 million for 2017. Guarantees On March 7, 2013 , we provided a guarantee to Archer on its payment obligations on certain financing arrangements. The maximum liability to Seadrill is limited to $100 million . The guarantee fee is 1.25% per annum. On July 31, 2013 , we provided Archer with an additional guarantee of $100 million , which was provided as part of Archer’s divestiture of a division, to support Archer’s existing bank facilities. During 2014, the guarantees above were increased to a total of $250 million . In April 2017 the guarantees were settled for $25 million reducing the guarantee balance to nil at December 31, 2017 (December 31, 2016: $25 million ). The guarantee fee was 1.25% per annum. On December 9, 2013 , we provided Archer Topaz Limited, a wholly owned subsidiary of Archer, with a guarantee of a maximum of EUR 48.4 million ( 2016 : EUR 48.4 million ), to support Archer’s credit facilities. The guarantee fee is 1.25% per annum. The guarantee was settled for $2.5 million in April 2017, reducing the guarantee balance to nil at December 31, 2017 (December 31, 2016: $25 million ) On February 5, 2014 , we provided Archer with a guarantee of a maximum of GBP 10 million , to support Archer’s leasing obligations of a warehouse for a period of 10 years . The guarantee outstanding as at December 31, 2017 was $10 million . ( 2016 : $10 million ). On July 14, 2014 , we provided Archer Norge AS, a wholly owned subsidiary of Archer, with a guarantee of a maximum of $20 million , to support Archer’s bank guarantee facility. The guarantee fee is 1.25% per annum. The guarantee was settled for $0.3 million in April 2017, reducing the guarantee balance to nil at December 31, 2017 (December 31,2016: $3 million ) We provide Archer Well Services, a wholly owned subsidiary of Archer, with a performance guarantee of a maximum of NOK 66.0 million , or $8.0 million to support Archer’s operations in Norway with a customer. The total guarantee fees charged to Archer for the year ended December 31, 2017 was $0.8 million ( 2016 : $3.9 million ; 2015 : $3.6 million ) respectively. These guarantee fees are included in "Other financial items and other income/(expense)" within the Consolidated Statement of Operations. Engineering Services Archer provides certain engineering services for us, and charged us fees of $0.1 million for the year ended December 31, 2017 ( 2016 : $1.0 million ; 2015 : $4.0 million ). These amounts are included in "Vessel and rig operating expenses" within the Consolidated Statement of Operations. SeaMex Limited As at March 10, 2015 , the date of deconsolidation, SeaMex Limited is considered to be a related party and not a controlled subsidiary of ours. Refer to Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information regarding the deconsolidation. The following is a summary of the related party agreements/transactions with SeaMex: Management and administrative service agreements In connection with the JV agreement, SeaMex, entered into a management support agreement with Seadrill Management, a wholly owned subsidiary of Seadrill, pursuant to which Seadrill Management provides SeaMex certain management and administrative services. The services provided by Seadrill Management are charged at cost plus management fee ranging from 4.5% to 8% . The agreement can be terminated by providing 60 days written notice. Income recognized under the management and administrative agreements for the year ended December 31, 2017 was $9 million , respectively ( 2016 : $7 million ; 2015 : $11 million ). It is also agreed that Seadrill Jack Up Operations De Mexico, which is a 100% owned subsidiary of SeaMex and provides support services to the rigs acquired by the JV, will continue to provide management services to Seadrill in respect of the rigs West Pegasus, West Freedom and West Castor and charge a fee ranging from of 4.85% to 8% plus costs incurred in connection with managing the rigs on its behalf. Seadrill Jack Up Operations De Mexico has charged us fees, under the above agreements for the year ended December 31, 2017 of $5 million ( 2016 : $5 million ; 2015 : $10 million ). These amounts are included within "Vessel and rig operating expenses". Loans $250 million Seller’s credit - In March 2015 , we provided SeaMex with a $250 million Seller’s credit as part of the settlement of the sale of assets to SeaMex. The Seller’s credit is divided into two facilities, (a) a term loan facility for an amount up to $230 million and (b) a revolving credit facility of up to $20 million . Both facilities bear interest at a rate of LIBOR plus a margin of 6.5% and mature in December 2019 . Interest on the Seller’s credit is payable quarterly in arrears. The loan facility is subordinated to SeaMex's external debt facility. The outstanding balance as at December 31, 2017 was $250 million ( 2016 : $250 million ). In 2015 we agreed to forgive accrued interest of $10 million against the Seller's credit in relation to the contract extension of the West Pegasus with Pemex. $162 million consideration receivable - SeaMex agreed to pay Seadrill an amount of $162 million being consideration receivable in relation to the sale of the West Titania to the Joint Venture. This amount was paid in full during July 2015 . $45 million loan facility - In November 2016, the terms attached to the $45.0 million funding from Seadrill were formalized, with an effective date of May 2015. The funding was provided on formation of the JV to fund short term working capital requirements. The facility bears interest at a rate of LIBOR plus a margin of 6.5% payable quarterly in arrears. The loan facility is subordinated to SeaMex's external debt facility. In the year ended December 31, 2015 the $45 million was classified within "Short-term amounts due from related parties" on the Consolidated Balance Sheet as there were no formal terms. In the year ended December 31, 2016, upon formalization this was reclassified to "Long-term amounts due from related parties" on the Consolidated Balance Sheet. Seadrill has made available a fully-subordinated unsecured credit facility of $20 million which will expire at the anniversary of the first draw-down of this amount or a portion thereof. The facility is to be provided by both Seadrill and Fintech at a ratio of 50% each. This matured at the end of December 2016 . The facility bore interest at a rate of LIBOR plus a margin of 6.5% . The facility was intended to be repayable once SeaMex had complied with certain conditions with regards to its lenders, however remained undrawn. Interest income for the year ended December 31, 2017 for these loans was $28 million ( 2016 : $18 million ; 2015 : $17 million ). Capital contributions During the year ended December 31, 2015 both the joint venture partners each made an additional $19 million of equity investment in SeaMex while retaining their 50% share in the joint venture. Guarantees During the latter part of 2015, SeaMex experienced issues regarding the delayed payment of invoices by its sole customer. The customer deferred payment into 2016 and SeaMex has since recovered the overdue balances. In order to ease the resulting cash flow impact on SeaMex, we, along with Fintech, our joint venture partner, agreed to provide certain support to SeaMex. Simultaneously, the lenders to SeaMex have provided a short-term amendment to the bank facility to provide some additional flexibility. In December 2015 , we and Fintech provided a joint and several guarantee for potential prepayment deficits that SeaMex might face under its loan agreements. The total guarantee for the potential prepayment deficits based on the December 31, 2015 testing date was $51 million . No liability was recognized for this guarantee as we did not consider it probable for the guarantee to be called. This joint and several guarantee was released in September 2016 as part of SeaMex's recent amendment to the bank facility. In respect of the guarantees and facilities described above, Seadrill has also obtained an indemnity from Fintech in order to be able to recover up to 50% of funding and costs, should Seadrill be called to make a contribution greater than its 50% share. Seadrill has also provided performance guarantees for the SeaMex drilling units, up to a total of $30 million as at December 31, 2017 ( 2016 : $30 million ) Receivables and Payables Receivables and payables with the SeaMex JV are comprised of management fees, advisory and administrative services, and other items including accrued interest. Receivables and payables are unsecured and generally settled quarterly in arrears in the ordinary course of business. Receivables/(payables) with SeaMex Joint Venture as at December 31, 2017 consisted of the following: (In $ millions) December 31, 2017 December 31, Seller’s credit 250 250 $45 million loan facility 45 45 Interest on long-term funding and sellers credit 50 22 Other receivables 32 31 Other payables (3 ) (2 ) Seabras Sapura transactions Seabras Sapura Participacoes S.A. and Seabras Sapura Holding GmbH, together referred to as Seabras Sapura, are joint ventures each indirectly owned 50% by us, and 50% by TL Offshore Sdn Bhd, a subsidiary of SapuraKencana. Yard guarantees We had provided yard guarantees in relation to Seabras Sapura Holding GmbH pipe-laying vessels which have been provided on a 50 :50 basis with TL Offshore. As at December 31, 2017 and December 31, 2016 there were no guarantees outstanding as construction of the final vessel was completed during the second quarter of 2016. Loans In May 2014 , we entered into a loan agreement with Sapura Navegaceo Martima S.A. of $10.8 million , which was novated to Seabras Sapura Participações S.A. on December 30, 2015 . The loan had an interest of 3.4% and was initially repayable by May 31, 2015 . On May 28, 2015 the maturity date for this loan was extended to May 31, 2016 . Subsequently, the loan agreement was amended and maturity date extended to February 28, 2017 . Subsequent to the year end, the maturity was extended to May 31, 2017 . As at June 30,2017, the loan agreement was amended and the debt is now repayable on demand. The outstanding balance as at December 31, 2017 was $11 million ( December 31, 2016 : $11 million ). In May 2014 , we entered into a loan agreement with Seabras Sapura of €3.25 million ( $4.5 million ). The loan had an interest of 3.4% and was repayable by May 31, 2015 . On May 28, 2015 the maturity date for this loan was extended to May 31, 2016 , however the loan was repaid in full in January 2016 . The outstanding balance as at December 31, 2017 was nil ( December 31, 2016 : $0 million ). In January 2015 , we provided a loan to Sapura Navegacao Martima S.A. of $18 million , which was novated to Seabras Sapura Participações S.A. on December 30, 2015 . The loan bears an interest rate of 3.4% and was initially repayable by February 16, 2016 . Subsequently, the loan agreement was amended and maturity date extended to February 28, 2017 . Subsequent to the year end, the maturity was extended to May 31, 2017 . As at June 30, 2017, the loan agreement was amended and the debt in now repayable on demand. The outstanding balance as at December 31, 2017 was $18 million ( December 31, 2016 : $18 million ). In April 2015 , we provided a loan to Sapura Onix GmbH of $14 million . The outstanding balance as at December 31, 2017 was $14 million ( December 31, 2016 : $14 million ). The loan bore an interest rate of LIBOR plus 3.99% and is repayable on demand, subject to certain restrictions under the agreement. In December 30, 2015 , we provided a loan to Seabras Sapura Participações S.A. of $3.3 million relating to the payments for equipment. The outstanding balance as at December 31

Risk management and financial i

Risk management and financial instruments (Restated)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Risk management and financial instruments (Restated)	Risk management and financial instruments The majority of gross earnings from our drilling units are receivable in U.S. dollars and the majority of our other transactions, assets and liabilities are denominated in U.S. dollars, the functional currency of ours. However, we have operations and assets in a number of countries worldwide and incur expenditures in other currencies, causing our results from operations to be affected by fluctuations in currency exchange rates, primarily relative to the U.S. dollar. Historically, we have been exposed to changes in interest rates on floating interest debt, and to the impact of changes in currency rates on NOK and SEK denominated debt. Due to the filing of the Bankruptcy Petitions, interest is no longer incurred on our unsecured bonds and they are held at the foreign exchange rate as at the Petition Date. Interest continues to be incurred on the floating interest debt but is recognized as an adequate protection payment for those facilities held as subject to compromise. Interest on floating rate debt not held as subject to compromise continues to be paid and recognized in the Consolidated Statement of Operations. There is thus a risk that interest rate fluctuations will have a positive or negative effect on the value of our cash flows. Prior to filing for Chapter 11, we entered into derivative agreements to mitigate the risk of currency and interest rate fluctuations. However, filing for Chapter 11 triggered an event of default under each of our International Swaps and Derivatives Agreements (ISDA). As a result, our counterparties terminated all outstanding transactions governed by the ISDA, effective September 13, 2017. The derivative transactions are recognized at the recoverable amount under the ISDA's as agreed with our lenders. As of December 31, 2017 we had $249 million in estimated derivative instrument settlements payable, reflected in the liabilities subject to compromise on the Consolidated Balance Sheet. Realized and unrealized gains and losses The total realized and unrealized gains and losses recognized in the Consolidated Statement of Operations relating to our derivative arrangements for the year ended December 31, 2017 , 2016 and 2015 are as follows: Year ended December 31, (In US$ millions) 2017 2016 2015 Gains / (losses) recognized in the Consolidated Statement of Operations relating to derivative financial instruments Interest rate swap agreements not qualified as hedge accounting (31 ) (48 ) (104 ) Cross currency interest rate swaps not qualified as hedge accounting 46 (20 ) (7 ) Foreign currency forwards not qualified as hedge accounting 1 — (9 ) TRS agreements — (6 ) (27 ) Other (5 ) — (3 ) Gain / (loss) on derivative financial instruments 11 (74 ) (150 ) Interest rate risk management Our exposure to interest rate risk relates mainly to our floating interest rate debt and balances of surplus funds placed with financial institutions. The exposure related to our floating interest debt has reduced since filing for Chapter 11, as noted above. We have historically managed this risk through the use of interest rate swaps and other derivative arrangements and continue to do so for some of our facilities which are not subject to compromise. Our objective is to obtain the most favorable interest rate borrowings available without increasing our foreign currency exposure. Surplus funds have generally been used to repay revolving credit facilities, or placed in accounts or fixed deposits with reputable financial institutions in order to maximize returns, while providing us with the flexibility to meet working capital and capital investments. The extent to which we utilized interest rate swaps and other derivatives to manage our interest rate risk has been determined by the net debt exposure. Interest rate swap agreements not qualified as hedge accounting At the date of filing for Chapter 11, we had interest rate swap agreements with an outstanding principal of $5,675 million ( December 31, 2016 : $6,372 million ). The agreements had maturity dates between November 2, 2017 and January 29, 2027 , swapping the floating element of interest on our facilities for fixed rates ranging between 0.74% and 3.34% . In addition we had an interest rate swap contract principal of $150 million ( December 31, 2016 : $162 million ), which was entered into in February 2014 with a forward start in March 2016, under which it pays a floating rate of LIBOR and receive a fixed rate of 2.12% . These agreements did not qualify for hedge accounting, and accordingly any changes in the fair values of the swap agreements are included in the Consolidated Statement of Operations under “Gain/(loss) on derivative financial instruments.” On September 13, 2017 the interest rate swaps were terminated under the ISDA and an adjustment for credit risk on the interest rate swap position was reversed to "Reorganization items, net" in the Consolidated Statement of Operations, totaling $18 million . The residual liability, represents the counterparty claimed value of $39 million , which was reclassified to liabilities subject to compromise in the Consolidated Balance Sheet as at December 31, 2017. As at December 31, 2016 we reported a gross liability of $64 million , net liability of $41 million , and an asset of $4 million . The asset and net liability as at December 31, 2016 was classified as "Other current assets" or "Other current liabilities" respectively in the Consolidated Balance Sheet. The total realized and unrealized losses recognized in the Consolidated Statement of Operations relating to interest rate swap agreements in 2017 amounted to $30 million ( 2016 : losses of $48 million , 2015 : losses of $104 million ). Cross currency interest rate swaps not qualified as hedge accounting At the date of filing for Chapter 11, we had outstanding cross currency interest rate swaps with principal amounts of $807 million ( December 31, 2016 : $807 million ) with maturity dates between March 2018 and March 2019 at fixed rates ranging from 4.94% to 6.18% . These agreements did not qualify for hedge accounting and accordingly any changes in the fair values of the swap agreements were included in the Consolidated Statement of Operations under “Gain/(loss) on derivative financial instruments”. On September 13, 2017 the cross currency interest rate swaps were terminated under the ISDA and an adjustment for credit risk on the interest rate swap position was reversed to "Reorganization items, net" in the Consolidated Statement of Operations, totaling $71 million . The residual liability represents the counterparty claimed value of $210 million , which was reclassified to liabilities subject to compromise in the Consolidated Balance Sheet as at December 31, 2017. The total fair value of cross currency interest swaps outstanding at December 31, 2016 amounted a gross and net liability of $194 million . The fair value of the cross currency interest swaps is classified as "Other current liabilities " in the Consolidated Balance Sheet as at December 31, 2016 . The total realized and unrealized gains recognized in the Consolidated Statement of Operations relating to cross currency interest rate swap agreements in 2017 amounted to $46 million ( 2016 : losses of $20 million , 2015 : losses of $7 million ). Interest rate hedge accounting A Ship Finance subsidiary consolidated by Seadrill as a VIE (refer to Note 34 "Variable Interest Entities"), has entered into interest rate swaps in order to mitigate the exposure to variability in cash flows for future interest payments on the loans taken out to finance the acquisition of the West Linus . These interest rate swaps qualify for hedge accounting under U.S. GAAP, and the instruments have been formally designated as a hedge to the underlying loan. When the hedge is effective, any changes in its fair value is included in “Other comprehensive income.” The effectiveness of hedging instruments is assessed at each reporting period. The total fair value of these interest rate swaps outstanding at December 31, 2017 amounted to an asset of $0 million ( December 31, 2016 : a liability of $1 million ), which are classified as "Other non-current assets " in the Consolidated Balance Sheet ( December 31, 2016 : "Other non-current liabilities"). Below is a summary of the notional amount, fixed interest rate payable and duration of the outstanding principal as at December 31, 2017 . Variable interest entity Outstanding principal as at December 31, 2017 Receive rate Pay rate Length of contract (In US$ millions) SFL Linus Limited (West Linus) 4.0 1 month LIBOR 2.01% Mar 2014 - Oct 2018 SFL Linus Limited (West Linus) 4.0 2 month LIBOR 2.01% Mar 2014 - Nov 2018 SFL Linus Limited (West Linus) 144.5 3 month LIBOR 1.77% Dec 2013 - Dec 2018 In the year ended December 31, 2017 the above VIEs recorded $1.2 million fair value gains on interest rate swaps ( December 31, 2016 : $1.1 million fair value gains). Any such gains or losses are recorded by those VIEs as “Other comprehensive income” but due to their ownership by Ship Finance these gains are allocated to “Non-controlling interest” in our Consolidated Statement of Changes in Shareholders' Equity. The net interest paid on these swaps for the year ended December 31, 2017 was $1 million ( 2016 : net interest paid of $2 million ). Any change in fair value resulting from hedge ineffectiveness is recognized immediately in earnings. The VIEs, and therefore we, recognized no gain or loss due to hedge ineffectiveness in the Consolidated Financial Statements during the twelve months ended December 31, 2017 ( December 31, 2016 : no fair value gain or loss, December 31, 2015 : no fair value gain or loss). Archer convertible debt instrument On April 26, 2017 Seadrill agreed with Archer to convert total outstanding subordinated loans, fees and interest provided to Archer, with a carrying value of $37 million , into a $45 million loan. The new loan receivable is a convertible debt instrument; the host is the debt and the convertible option an embedded derivative. The instrument is bifurcated with both elements initially and subsequently recognized at fair value. The fair value of the new loan receivable as at April 26, 2017 was $56 million , resulting in a $19 million gain on debt extinguishment in the statement of operations. The debt and embedded derivative option was revalued at December 31, 2017 , with Seadrill recognizing a fair value loss of $4 million on the embedded derivative and a $1m fair value gain on the loan receivable, bringing the total fair value of the convertible debt instrument as at December 31, 2017 to $52 million . Exposure to interest rate fluctuations As at December 31, 2017 , our net exposure to floating interest rate fluctuations on our outstanding debt was $0.2 billion , representing the outstanding debt balance on the AOD $360 million facility, which is not subject to compromise. The interest rate swaps associated with our debt which is classified as subject to compromise have been terminated so there is no fixed interest rate swaps outstanding to offset any movement in interest rate. A 1% change in short-term interest rates would therefore increase or decrease our net income by approximately $2 million . As at December 31, 2016 , our net exposure to floating rate fluctuations on our outstanding debt was $0.23 billion . This comprises our total net interest-bearing debt including related party debt of $9.9 billion , less the total notional principal of our floating to fixed interest rate swaps and cross-currency swaps of $7.4 billion , less the fixed interest loans of $2.27 billion . A 1% change in short-term interest rates would therefore have increased or decreased our net income by approximately $3 million in 2016 . Foreign exchange risk management We and the majority of our subsidiaries use the U.S. dollar as the functional currency because the majority of the revenues and expenses are denominated in U.S. dollars. Accordingly, our reporting currency is also U.S. dollars. We do, however, earn revenue and incur expenses in other currencies and there is thus a risk that currency fluctuations could have an adverse effect on the value of our cash flows. Prior to entering Chapter 11 we were exposed to the impact of changes in currency exchange rates on NOK and SEK denominated debt. Prior to September 13, 2017, we had entered into derivative agreements to mitigate the risk of exchange rate fluctuations as described below. Foreign currency forwards not qualified as hedge accounting Historically we have used foreign currency forward contracts and other derivatives to manage our exposure to foreign currency risk on certain assets, liabilities and future anticipated transactions. Such derivative contracts did not qualify for hedge accounting treatment and were recorded in the Consolidated Balance Sheet under "Other current assets" if the contracts had a net positive fair value, and under "Other current liabilities" if the contracts had a net negative fair value. At December 31, 2017 and December 31, 2016 , we had no outstanding currency forward contracts. The total realized and unrealized losses recognized in the Consolidated Statement of Operations relating to foreign currency forward agreements in 2017 amounted to nil ( 2016 : losses of nil , 2015 : losses of $9 million ). Exposure to exchange rate fluctuations At December 31, 2017 we had no debt exposure to exchange rate fluctuations as the NOK and SEK denominated debt facilities were held at the foreign exchange rate as at the filing date. At December 31, 2016 , a 1% change in the exchange rate between the U.S. dollar and Norwegian Krone (NOK) and Swedish Krona (SEK) would result in a fair value gain of $5.4 million on the NOK and SEK denominated interest bearing debt and a fair value loss of $5.5 million on the cross currency interest rate swaps that would be reflected in our Consolidated Statements of Operations, based on our cross currency interest rate swaps and currency forward contracts as at December 31, 2016 . Equity price risk management Total Return Swap (“TRS”) Agreements During 2016 and 2015 we entered into and settled various TRS agreements which are indexed to our own common shares. The settlement amount for the TRS transaction will be (A) the market value of the shares at the date of settlement plus all dividends paid by us between entering into and settling the contract, less (B) the reference price of the shares agreed at the inception of the contract plus the counterparty’s financing costs. Settlement will be either a payment by the counterparty to us, if (A) is greater than (B), or a payment by us to the counterparty, if (B) is greater than (A). There is no obligation for us to purchase any shares under the agreement and this arrangement has been recorded as a derivative transaction, with the fair value of the TRS recognized as an asset or liability as appropriate, and changes in fair values recognized in the Consolidated Statement of Operations. On September 5, 2016, we settled TRS agreements for 4,000,000 Seadrill Limited shares at a strike price of NOK 20.30 . As at December 31, 2017 there were no outstanding TRS agreements ( December 31, 2016 : no outstanding TRS agreements). The total realized and unrealized losses recognized in the Consolidated Statement of Operations relating to TRS agreements in 2017 was nil ( 2016 : losses of $6 million , 2015 : losses of $27 million ). Sevan share repurchase agreements During 2013 we entered into agreements in which we had sold our shares in Sevan Drilling to commercial banks and then entered into a share purchase agreement to repurchase the same amount of shares at a later date which is generally within three months from the date of entering into the sale agreement. As at December 31, 2014 we had agreements for 216,065,464 Sevan Drilling ASA shares at a strike price of NOK 4.1701 and 81,828,500 Sevan Drilling ASA shares at a strike price of NOK 4.1966 . On February 6, 2015 , these forward agreements were settled and new forward agreements were entered into. The cash settlement was NOK135 million . On May 6, 2015, we rolled forward the agreement and entered into a forward agreement for 216,065,464 Sevan shares expiring August 10, 2015 with a strike price of NOK 0.6247 , and a second forward agreement for 81,828,500 Drilling ASA shares expiring August 6, 2015 with a strike price of NOK 0.6243 . As part of the Sevan Drilling group’s internal reorganization program effective from June 30, 2015 the parent company of the Sevan Drilling group was migrated from Sevan Drilling ASA, a Norwegian registered entity, to Sevan Drilling Limited, a Bermudan registered entity. As part of the restructuring, shareholders on the Oslo Stock Exchange listed entity were distributed shares in the Bermudan entity on a 20 :1 basis. The Norwegian entity was then delisted from the Oslo Stock Exchange, and the Bermudan entity was listed in its place, maintaining the ticker “SEVDR.” Accordingly, the outstanding share repurchase agreements mentioned above were settled for consideration paid of $4 million , and we completed the repurchase of the 297,893,964 shares in Sevan Drilling ASA at a value equal to the nominal value of the shares. Simultaneously new agreements were taken out to repurchase 14,894,699 shares in Sevan Drilling Limited with the same banks. On November 6, 2015, we settled the forward agreement for 10,803,274 shares in Sevan Drilling Limited at a strike price of NOK 8.9482 and settled the forward agreement for 4,091,425 shares for a strike price of NOK 8.5539 . The total amount paid on settlement was $16,000,000 . As a result of these transactions, we maintained a controlling interest in the Sevan Drilling group, and as a result the Sevan Drilling group remains consolidated in our Consolidated Financial Statements. As at December 31, 2015 these agreements were fully settled. SapuraKencana share agreements and financing On September 18, 2013, we entered into two derivative contract agreements with a commercial bank which enabled us to obtain financing against a portion of our equity investment in SapuraKencana in which we received $250 million upfront as prepayment for one of the agreements. The agreements have a settlement date three years from the inception date and include an interest equivalent component which is based on the prepaid amount received and LIBOR plus 1.90% per annum. On July 8, 2015, we amended the financing arrangement relating to our equity investment in SapuraKencana and extended the agreement to July 2018. The total financing was reduced by $90 million to $160 million , and the corresponding restricted cash held as collateral of $93 million was settled against the liability. In addition, the interest rate increased to LIBOR plus 2.6% . As at December 31, 2015 we had associated restricted cash of $160 million due to the significant fall in the share price of SapuraKencana. On February 24, 2016 , we elected to exercise the optional termination notice under the prepaid forward and equity swap agreements, and the corresponding liability of $160 million and restricted cash of $160 million were settled, and the pledged security was released. The amount pledged as security at December 31, 2015 was $195 million , which has been presented as a long term marketable security on the Consolidated Balance Sheet (see Note 13 "Marketable Securities" to the Consolidated Financial Statements included herein). On April 27, 2016 , we sold our entire shareholding in SapuraKencana for net proceeds of $195 million , net of transaction costs. Fair values of financial instruments The carrying value and estimated fair value of our financial instruments that are not measured at fair value on a recurring basis at December 31, 2017 and December 31, 2016 are as follows: Financial assets December 31, 2017 December 31, 2016 (In US$ millions) Fair value Carrying value Fair value Carrying value Cash and cash equivalents 1,255 1,255 1,368 1,368 Restricted cash 104 104 75 75 Related party loans receivable - short term 25 25 174 174 Related party loans receivable - long term 522 515 487 487 Financial liabilities As at December 31, 2017 , we had outstanding floating rate interest bearing debt with carrying value of $6,367 million , of which $5,371 million was held as subject to compromise. As a result of filing for Chapter 11, the fair value of our floating rate interest bearing debt cannot be reasonably determined. As at December 31, 2016 our floating rate interest bearing debt had carrying value of $7,333 million and fair value of $6,542 million . As at December 31, 2017 , we had outstanding fixed and floating interest bonds with carrying value of $1,735 million and $599 million respectively. These were held as a liability subject to compromise on the Consolidated Balance Sheet. As a result of filing for Chapter 11, the fair value of our floating rate interest bearing debt cannot be reasonably determined. As at December 31, 2016 our fixed interest bonds had carrying value of $1,735 million and fair value of $766 million and our floating interest bonds had carrying value of $540 million and fair value of $223 million . As at December 31, 2017 , we had outstanding related party fixed rate debt with carrying value of $314 million and fair value of $218 million ( December 31, 2016 : carrying value of $415 million and fair value of $242 million ). At December 31, 2017 we had $39 million of interest rate swaps and $210 million of cross currency interest rate swaps classified as liabilities subject to compromise. The balance reflects the terminated value claimed by the counterparty as at September 13, 2017. As a result, the carrying and fair value of the financial instrument as at December 31, 2017 would be $249 million . This was previously measured at level 1 on the fair value measurement hierarchy, see table below. Fair value considerations U.S. GAAP emphasizes that fair value is a market-based measurement, not an entity-specific measurement, and should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, U.S. GAAP establishes a fair value hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within levels 1 and 2 of the hierarchy) and the reporting entity’s own assumptions about market participant assumptions (unobservable inputs classified within level 3 of the hierarchy). Level 1 input utilizes unadjusted quoted prices in active markets for identical assets or liabilities that we have the ability to access. Level 2 inputs are inputs other than quoted prices included in level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability, other than quoted prices, such as interest rates, foreign exchange rates and yield curves that are observable at commonly quoted intervals. Level 3 inputs are unobservable inputs for the asset or liability, which are typically based on an entity’s own assumptions, as there is little, if any, related market activity. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability. The carrying value of cash and cash equivalents and restricted cash, which are highly liquid, is a reasonable estimate of fair value and categorized at level 1 on the fair value measurement hierarchy. The fair value of the related party loans receivable from Seadrill Partners, Seabras Sapura and SeaMex are estimated to be equal to the carrying value. This debt is not freely tradable and cannot be recalled by us at prices other than specified in the loan note agreements. The loans were entered into at market rates. They are categorized as level 2 on the fair value measurement hierarchy. Other trading balances with related parties are not shown in the table above and are covered under Note 30 "Related party transactions". The fair value of other trading balances with related parties are also assumed to be equal to their carrying value. The related party convertible loan receivable from Archer has been fair valued for the straight debt and conversion option components. We have categorized this at level 3 on the fair value measurement hierarchy. The fair value of the loans provided by Ship Finance to our VIE’s are derived using the Discounted Cash Flow (DCF) model. The cost of debt of 11% was used to estimate the present value of the future cash flows. We have categorized this at level 2 on the fair value measurement hierarchy. Refer to Note 30 "Related party transactions" for further information. Financial instruments that are measured at fair value on a recurring basis: Fair value Fair value measurements at reporting date using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs (In US$ millions) December 31, 2017 (Level 1) (Level 2) (Level 3) Assets: Marketable securities - current asset 124 124 — — Convertible debt instrument - non-current asset 52 — — 52 Total assets 176 124 — 52 Fair value Fair value measurements at reporting date using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs (In US$ millions) December 31, 2016 (Level 1) (Level 2) (Level 3) Assets: Marketable securities - current assets 110 110 — — Interest rate swap contracts – non-current assets 4 — 4 — Total assets 114 110 4 — Liabilities: Interest rate swap contracts – current liabilities 41 — 41 — Interest rate swap contracts – non-current liabilities 1 — 1 — Cross currency interest rate swap contracts – current liabilities 194 — 194 — Total liabilities 236 — 236 — Quoted market prices are used to estimate the fair value of marketable securities, which are valued at fair value on a recurring basis. The fair values of interest rate swaps, cross currency interest rate swaps, and forward exchange contracts as at December 31, 2016 are calculated using well-established independent valuation techniques, applied to contracted cash flows and expected future LIBOR and NIBOR interest rates, and counterparty non-performance credit risk assumptions. The calculation of the credit risk in the swap values is subject to a number of assumptions including an assumed credit default swap rate based on our traded debt, and recovery rate, which assumes the proportion of value recovered, given an event of default. We have categorized these transactions as level 2 on the fair value measurement hierarchy. Retained Risk a) Physical Damage Insurance We purchase hull and machinery insurance to cover physical damage to our drilling units. We retain the risk for the deductibles relating to physical damage insurance on our fleet which is currently a maximum of $5 million per occurrence. b) Loss of Hire Insurance We purchase insurance to cover for loss of revenue for our operational rigs in the event of extensive downtime caused by physical damage to our drilling units where such damage is covered under our physical damage insurance. The loss of hire insurance has a deductible period of 60 days after the occurrence of physical damage. Thereafter, insurance policies according to which we are compensated for loss of revenue are limited to 290 days per event and aggregated per year. The daily indemnity will vary from 75% to 100% of the contracted dayrate. We retain the risk related to loss of hire during the initial 60 day period, as well as any loss of hire exceeding the number of days permitted under the insurance policy. If the repair period for any physical damage exceeds the number of days permitted under the loss of hire policy, we will be responsible for the costs in such period. c) Protection and Indemnity Insurance We purchase protection and indemnity insurance and excess liability for personal injury liability for crew claims, non-crew claims and third-party property damage including oil pollution from the drilling units to cover claims of up to $750 million per event and in the aggregate. We retain the risk for the deductible of up to $25,000 per occurrence relating to protection and indemnity insurance, or up to $500,000 for claims made in the United States. d) Windstorm Insurance We have elected to place an insurance policy for physical damage to rigs and equipment caused by named windstorms in the U.S. Gulf of Mexico with a Combined Single Limit of $100 million in the annual aggregate, which includes loss of hire. We intend to renew our policy to insure a limited part of this windstorm risk for a further period starting May 1, 2018 through April 30, 2019. Credit risk We have financial assets, including cash and cash equivalents, marketable securities, other receivables and certain amounts receivable on derivative instruments, mainly forward exchange contracts and interest rate swaps. These assets expose us to credit risk arising from possible default by the counterparty. We consider the counterparties to be creditworthy financial institutions and does not expect any significant loss to result from non-performance by such counterparties. We, in the normal course of business, do not demand collateral. The credit exposure of interest rate swap agreements, currency option contracts and foreign currency contracts is represented by the fair value of contracts with a positive fair value at the end of each period, reduced by the effects of master netting agreements, adjusted for counterparty non-performance credit risk assumptions. It is our policy to enter into master netting agreements with the counterparties to derivative financial instrument contracts, which give us the legal right to discharge all or a portion of amounts owed to a counterparty by offsetting them against amounts that the counterparty owes to us. Concentration of risk We have financial assets, including cash and cash equivalents, marketable securities, other receivables and certain derivative instrument receivable amounts. These other assets expose us to credit risk arising from possible default by the counterparty. There is also a concentration of credit risk with respect to cash and cash equivalents to the extent that most of the amounts are carried with Citibank, Nordea Bank Finland Plc, Danske Bank A/S, BNP Paribas and ING Bank N.V. We consider these risks to be remote. For details on the customers with greater than 10% of contract revenues, refer to Note 4 "Segment information".

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies Legal Proceedings From time to time we are a party, as plaintiff or defendant, to lawsuits in various jurisdictions for demurrage, damages, off-hire and other claims and commercial disputes arising from the construction or operation of our drilling units, in the ordinary course of business or in connection with our acquisition or disposal activities. We believe that the resolution of such claims will not have a material impact individually or in the aggregate on our operations or financial condition. Our best estimate of the outcome of the various disputes has been reflected in our Consolidated Financial Statements as at December 31, 2017 . Class action In December 2014, a purported shareholder class action lawsuit, Fuchs et al. v. Seadrill Limited et al., No. 14-cv-9642 (LGS)(KNF), was filed in U.S. Federal District Court in the Southern District of New York, alleging, among other things, that Seadrill and certain of our executives made materially false and misleading statements in connection with the payment of dividends. In January 2015, a second purported shareholder class action lawsuit, Heron v. Seadrill Limited et al., No. 15-cv-0429 (LGS)(KNF), was filed in the same court on similar grounds. In March 2015, a third purported shareholder class action lawsuit, Glow v. Seadrill Limited et al., No. 15-cv-1770 (LGS)(KNF), was filed in the same court on similar grounds. On March 24, 2015, the court consolidated these complaints into a single action. On June 23, 2015 the court appointed co-lead plaintiffs and co-lead counsel and ordered the co-lead plaintiffs to file a single consolidated amended complaint by July 23, 2015. The amended complaint was filed on July 23, 2015 alleging, among other things, that Seadrill, North Atlantic Drilling Ltd and certain of their executives made materially false and misleading statements in connection with the payment of dividends, the failure to disclose the risks to the Rosneft transaction as a result of various enacted government sanctions and the inclusion in backlog of $4.1 billion attributable to the Rosneft transaction. The defendants filed their Motion to Dismiss the Complaint on October 13, 2015. The plaintiffs, in turn, filed their Opposition to the Motion to Dismiss on November 12, 2015 and the defendants’ Reply Brief was served on December 4, 2015. Although we intend to vigorously defend this action, we cannot predict the outcome of this case, nor can we estimate the amount of any possible loss. Accordingly, no loss contingency has been recognized within the Consolidated Financial Statements. West Mira On October 12, 2015, HSHI launched arbitration proceedings with regard to Seadrill’s cancellation of the West Mira construction contract. This was settled on March 13, 2017 with an agreed yard installment payment of $170 million was received from HSHI in March 2017. For further information refer to Note 6 "(Loss)/gain on disposals.” Sevan Drilling Sevan Drilling is a majority-owned subsidiary of ours. On June 29, 2015, Sevan Drilling disclosed that it had initiated an internal investigation into activities with an agent under certain drilling contracts with Petrobras in Brazil, which were entered prior to the separation from the Sevan Marine Group. On October 16, 2015, Sevan Drilling further disclosed that Sevan Drilling ASA, previously the parent company of Sevan Drilling, had been accused of breaches of Sections 276a and 276b of the Norwegian Criminal Code in respect of payments made in connection with the performance during 2012 to 2015 of drilling contracts originally awarded by Petrobras to Sevan Marine ASA in the period between 2005–2008. For further details please see the Sevan Drilling Annual Report and Financial Statements for the Year Ended December 31, 2017, and subsequent quarterly financial statements as they become publicly available. We cannot predict whether any other governmental authority will seek to investigate this matter, or if a proceeding were to be opened, the scope or ultimate outcome of any such investigation and as a result no loss contingency has been recognized in Seadrill’s Consolidated Financial Statements. NADL In February 2016 North Atlantic Drilling was notified of certain customer claims. The client withheld amounts from invoice payments due in the first quarter of 2016, which were settled in January 2017 for $34.7 million subsequent to the Consolidated Balance Sheet date. The settlement amount was reflected as at December 31, 2016. North Atlantic Drilling, and all other offshore contractors that are members of the Norwegian Shipowners’ Association, lost a Norwegian court case in July 2015 concerning the pension rights of night shift compensation for offshore workers. The case was appealed to the Supreme Court of Norway and the hearing was held in June 2016. The Supreme Court of Norway ruled in favor of the members of the Norwegian Shipowners’ Association, and as such we do not consider there to be any remaining contingent liability. Accordingly, no loss contingency has been recognized within our Consolidated Financial Statements as at December 31, 2016 or December 31, 2017 . Seabras Sapura joint venture The Sapura Esmeralda, operates under a temporary Brazilian flag which expires on July 28, 2018. Seabras Sapura is currently in the process of applying for a registration with Brazilian authorities which will either entitle the vessel to permanently fly the Brazilian flag or extend the expiry of the temporary flag. There is a risk that either no permanent right to fly the Brazilian flag will be obtained, or that the temporary flag will either be revoked or not be renewed. If this were to happen, it is likely to affect the operations of the Sapura Esmeralda, which could in turn affect its commercial agreements and related financing. Patent infringement In January 2015, a subsidiary of Transocean Ltd. filed suit against certain of our subsidiaries for patent infringement. The suit alleges that one of our drilling rigs that operate in the U.S. Gulf of Mexico violated Transocean patents relating to dual-activity drilling. In the same year, we challenged the validity of the patents via the Inter Partes Review process within the U.S. Patent and Trademark Office which ultimately stayed the litigation. The IPR board held in March 2017 that the patents were valid. Despite this finding, we do not believe that our rigs infringe the Transocean patents, which have now expired, and we continue to defend ourselves vigorously against this suit. We do not believe that the ultimate liability, if any, resulting from this litigation will have a material effect on our financial position. We have not previously recognized any related loss contingency in our Consolidated Financial Statements as of December 31, 2017 as we do not believe the loss to be probable. Pledged assets The book value of assets pledged under secured credit facilities as of December 31, 2017 was $12,933 million ( 2016 : $13,927 million ). At December 31, 2017 we had no marketable securities pledged as security for certain derivative arrangements ( 2016 : nil ). Purchase Commitments At December 31, 2017 , we had contractual commitments under nine newbuilding contracts totaling $1,685 million ( 2016 : thirteen newbuilding contracts totaling $4,098 million ). As part of the Chapter 11 proceedings, the Debtors negotiated and announced a global settlement with various creditors, including Samsung Heavy Industries Co., Ltd. ("Samsung") and Daewoo Shipbuilding & Marine Engineering Co., Ltd ("DSME"). The global settlement included an agreement regarding the allowed claim of the newbuild shipyards Samsung and DSME, and the Debtors’ rejection and recognized termination of the newbuild contracts for the West Dorado , West Draco , West Aquila and the West Libra . In addition, the newbuilding commitments for the Sevan Developer had previously had a contractual obligation balance of $480 million at December 31, 2016. This increased to $526 million in 2017 but was subsequently derecognized in April 2017 as Sevan was deemed to have lost control of the asset and therefore derecognized the newbuild asset and construction obligation. Refer to Note 6 " Loss on disposals " for further information. The remaining purchase commitments are mainly yard installments and are for the construction of eight jack-up rigs. The table below shows the maturity schedule for the newbuilding contractual commitments, which reflects the most recent deferral agreements with Dalian. Refer to Note 3 "Chapter 11 Proceedings" for further information. (In US$ millions) 2018 2019 2020 2021 2022 2023 and thereafter Total Newbuilding commitments 1,685 — — — — — 1,685 Guarantees We have issued guarantees in favor of third parties as follows, which is the maximum potential future payment for each type of guarantee: (In US$ millions) December 31, 2017 December 31, 2016 Guarantees in favor of customers 1, 2 ,3 1,213 1,403 Guarantees in favor of banks 1, 2, 3, 4 698 1,677 Guarantees in favor of suppliers 1, 3, 4 2,200 2,600 Total 4,111 5,680 (1) Guarantees to Seadrill Partners - Within guarantees in favor of customers are guarantees provided on behalf of Seadrill Partners of $165 million ( 2016 : $185 million ). After the insulation of Seadrill Partners from Seadrill in August 2017 there were no guarantees in favor of banks provided on behalf of Seadrill Partners ( 2016 : $621 million ). Guarantees in favor of suppliers includes guarantees on behalf of Seadrill Partners of $0.6 million ( 2016 : $0.4 million ). Refer to Note 30 "Related party transactions" for more information. (2) Guarantees to SeaMex - Within guarantees in favor of customers are guarantees provided on behalf of SeaMex of $30 million ( 2016 : $30 million ). Guarantees in favor of banks includes guarantees on behalf of SeaMex of nil ( 2016 : $0 million ). Refer to Note 30 "Related party transactions" for more information. (3) Guarantees to Archer - Within guarantees provided to customers are guarantees provided on behalf of Archer of $8 million ( 2016 : $8 million ). There were no guarantees in favor of banks provided on behalf of Archer as at December 31, 2017 as these were settled during the year ( 2016 : $253 million and EUR 24 million ( $25 million )). Guarantees in favor of suppliers include guarantees on behalf of Archer of GBP 7 million ( $10 million ) ( 2016 : GBP 8 million ( $10 million )). As of December 31, 2016 , we recognized a $28 million contingent liability to reflect the potential cash settlement of the guarantees. Refer to Note 30 "Related party transactions" for more information. (4) Guarantees to Seabras Sapura - Within guarantees in favor of banks are guarantees provided on behalf of Seabras Sapura Participacoes and Seabras Sapura Holdco totaling $698 million ( 2016 : $787 million ). There were no guarantees in favor of suppliers in relation to our joint venture Seabras Sapura Holdco ( 2016 : nil ). Refer to Note 30 "Related party transactions" for more information. As of the Consolidated Balance Sheet date, except for where specifically stated above, we have not recognized any liabilities for the above guarantees, as we do not consider it is probable for the guarantees to be called.

Operating leases

Operating leases	12 Months Ended
	Dec. 31, 2017
Leases, Operating [Abstract]
Operating leases	Operating leases We have operating leases relating to our premises, the most significant being our offices in London, Liverpool, Oslo, Stavanger, Singapore, Houston, Rio de Janeiro and Dubai. In the years ended December 31, 2017 , 2016 and 2015 rental expenses amounted to $19 million , $17 million and $23 million , respectively. Future minimum rental payments are as follows: Year (In US$ millions) 2018 12 2019 8 2020 7 2021 7 2022 5 2023 and thereafter 1 Total 40

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2017
Variable Interest Entity, Measure of Activity [Abstract]
Variable Interest Entities	Variable Interest Entities As at December 31, 2017 , we leased two semi-submersible rigs, and a jack-up rig from VIEs under capital leases. Each of the units had been sold by us to single purpose subsidiaries of Ship Finance and simultaneously leased back by us on bareboat charter contracts for a term of 15 years . We have several options to repurchase the units during the charter periods, and obligations to purchase the assets at the end of the 15 years lease period. On June 28, 2013, our consolidated subsidiary NADL sold the entity that own the jack-up, the West Linus , to the Ship Finance subsidiary, SFL Linus Ltd. The purchase consideration reflected a market value of the rig as at the delivery date which was $600 million . This rig was simultaneously chartered back to us over a period of 15 years . Upon closing of the purchase, SFL Linus Ltd received a $195 million loan from Ship Finance which bears an interest of 4.5% per annum and matures in 2029 . During 2014 the loan was reduced to $125 million , and is reported as long-term debt due to related parties in our Consolidated Balance Sheet as at December 31, 2017 and December 31, 2016 . The following table gives a summary of the sale and leaseback arrangements and repurchase options from VIEs, as at December 31, 2017 : Unit Effective from Sale value (In US$ millions) First repurchase option (In US$ millions) Month of first repurchase option Last repurchase option (1) (In US$ millions) Month of last repurchase Option (1) West Taurus Nov 2008 850 418 Feb 2015 149 Nov 2023 West Hercules Oct 2008 850 580 Aug 2011 135 Aug 2023 West Linus June 2013 600 370 Jun 2018 170 Jun 2028 (1) Ship Finance has a right to require us to purchase the West Linus rig on the 15th anniversary for the price of $100 million if we don’t exercise the final repurchase option. We have determined that the Ship Finance subsidiaries, which own the units, are VIEs, and that we are the primary beneficiary of the risks and rewards connected with the ownership of the units and the charter contracts. Accordingly, these VIEs are fully consolidated in our Consolidated Financial Statements. The equity attributable to Ship Finance in the VIEs is included in non-controlling interests in our Consolidated Financial Statements. At December 31, 2017 and at December 31, 2016 the units are reported within drilling units in our balance sheet. We did not record any gains from the sale of the units, as they continued to be reported as assets at their original cost in our consolidated balance sheet at the time of each transaction. The investment in capital lease amounts are eliminated on consolidation against the corresponding capital lease liability held within Seadrill entities. The remainder of assets and liabilities of the VIEs are fully reflected within the Consolidated Financial Statements. The bareboat charter rates are set on the basis of a Base LIBOR Interest Rate for each bareboat charter contract, and thereafter are adjusted for differences between the LIBOR fixing each month and the Base LIBOR Interest Rate for each contract. A summary of the average bareboat charter rates per day for each unit is given below for the respective years. (In US$ thousands) 2017 2018 2019 2020 2021 2022 West Taurus 158 158 144 143 136 135 West Hercules 170 166 143 141 135 135 West Linus 222 222 173 140 140 133 The assets and liabilities in the statutory accounts of the VIEs as at December 31, 2017 and as at December 31, 2016 are as follows: (In US$ millions) December 31, 2017 December 31, 2016 SFL SFL SFL SFL SFL SFL Name of unit West Taurus West Hercules West Linus West Taurus West Hercules West Linus Investment in finance lease 335 326 431 365 360 483 Amount due from related parties 4 4 — 4 4 — Other assets (1) 6 6 8 2 2 — Total assets 345 336 439 371 366 483 Short-term interest bearing debt 226 27 48 23 28 51 Long-term interest bearing debt — 224 261 226 251 305 Other liabilities 3 2 — 3 1 1 Short-term debt due to related parties — — 4 — — — Long-term debt due to related parties (2) 113 80 121 119 86 126 Total liabilities 342 333 434 371 366 483 Equity 3 3 5 — — — Book value of units in the Company's consolidated accounts 385 508 515 409 537 537 (1) Includes cash balance of $17 million as at December 31, 2017 ( December 31, 2016 : nil ). These have been consolidated into the Consolidated Balance Sheet within "Cash and cash equivalents". (2) We present balances due to/from Ship Finance on a net basis, due to the fact that there is a right to offset established in the long-term loan agreements, and the balances are intended to be settled on a net basis. As at December 31, 2016 , the balances offset were $26 million related to SFL Deepwater Ltd and $59 million related to SFL Hercules Ltd against "Long term debt due to related parties" within "Non-current liabilities" in the Consolidated Balance Sheet. As at December 31, 2017 , we have no receivable balances presented against "Long term debt due to related parties" within "Non-current liabilities" in the Consolidated Balance Sheet. In the period ended December 31, 2017 the VIEs declared and paid dividends totaling $14 million ( December 31, 2016 : $113 million ).

Assets held for sale

Assets held for sale	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Assets held for sale	Assets held for sale On December 2, 2015, we signed an amendment with Jurong Shipyard (“Jurong”) for the deferral of the delivery of the semi-submersible drilling unit, the West Rigel (the “Unit”). The deferral period originally lasted until June 2, 2016, but was then subsequently extended to July 6, 2018. Following completion of the deferral period, we and Jurong agreed to form a Joint Asset Holding Company for joint ownership of the Unit, 23% to be owned by us and 77% by Jurong, in the event no employment was secured for the Unit and no alternative transaction is completed. Until the end of the deferral period, we would continue to market the unit for an acceptable drilling contract, and the Unit was to remain at the Jurong Shipyard in Singapore. We and Jurong also considered other commercial opportunities for the Unit during this period. On December 26, 2017, Jurong announced that a sale agreement, subject to conditions has been signed for West Rigel . As the agreement is pursuant to conditions being met, we will continue to hold the asset within "Non-current assets held for sale". On April 5, 2018, we entered into a settlement and release agreement, subject to Bankruptcy Court approval, with Jurong in respect of the West Rigel whereby we agreed that the share of sale proceeds from the sale of the West Rigel by Jurong would be $126 million . We consider that this agreement provides additional evidence for the value of the asset held for sale at December 31, 2017, and have therefore reflected the agreed share of proceeds in the sales value of the asset held for sale at the balance sheet date, recognizing a $2 million loss on disposal. (In US$ millions) As at December 31, 2017 As at December 31, 2016 Opening balance at the beginning of the period 128 128 West Rigel newbuild investment, classified as held for sale — — Loss on disposal (2 ) — Non-current assets held for sale 126 128

Supplementary cash flow informa

Supplementary cash flow information	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Supplementary cash flow information	Supplementary cash flow information The table below summarizes the non-cash investing and financing activities relating to the periods presented: December 31, 2017 December 31, 2016 December 31, 2015 Non-cash investing activities Disposal of subsidiaries - existing bank loan repaid (1) — — 150 Sale of rigs and equipment (2) 103 — — Increase of investment in Seadrill Mobile Units (Nigeria) Ltd (7) — (6 ) — Proceeds from repayment of short-term loan from related parties due to Seadrill Partners insulation from Seadrill Limited (9) 109 — — Derecognition of Sevan Developer newbuild asset (10) 620 — — Derecognition of Sevan Developer construction obligation (10) (526 ) — — Non-cash financing activities Repayment of bank loan through disposal of subsidiaries (1) — — (150 ) Repayment of debt following sale of rigs and equipment (2) (103 ) — — Repayment relating to share forward contracts and other derivatives (3) — — (136 ) Repayment relating to SapuraKencana financing agreements (4) — (160 ) (93 ) Conversion of convertible bond into shares, decrease in long term debt (5) — (105 ) — Conversion of convertible bond into shares, net increase in equity (5) — 58 — Increase in non-controlling interest in Seadrill Nigeria Operations Ltd (6) — 7 — Proceeds from long-term loans (7) — 150 — Long term loans netted-down with related party balances (7) — (150 ) — Dividend to non-controlling interests in VIEs (8) (14 ) (113 ) — Repayment of debt following insulation of Seadrill Partners from Seadrill Limited (9) (109 ) — — 1. During the year ended December 31, 2015 , existing debt of ours was directly settled as consideration for the disposal of certain drilling rigs to the SeaMex joint venture - refer to Note 6 "(Loss)/gain on disposals" for further information. 2. During the year ended December 31, 2017 , we completed our sale of the West Triton, West Resolute and West Mischief to Shelf Drilling , receiving cash consideration of $122 million . This comprised sales value of $225 million offset by $103 million of debt repayments. Refer to Note 6 "(Loss)/gain on disposals" for further information. 3. During the year ended December 31, 2015 , we settled Sevan share repurchase agreements using cash balances already classified as restricted. 4. During the years ended December 31, 2016 and December 31, 2015 , we settled SapuraKencana financing agreements using cash balances already classified as restricted. 5. In May 2016 , we entered into a privately negotiated exchange agreement with certain holders of our outstanding 5.625% (subsequently increased to 6.125% ) Senior Notes due in 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 8,184,340 new shares of our common stock, par value $2.00 per share, in exchange for $55 million principal amount of the 2017 Notes. Settlement occurred on May 20, 2016 , upon which we had a total of 500,944,280 shares of our common stock issued and outstanding. In June 2016 , we entered into another privately negotiated exchange agreement with certain holders of our outstanding 5.625% (subsequently increased to 6.125% ) Senior Notes due 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 7,500,000 new shares of our common stock, par value $2.00 per share, in exchange for $50 million principal amount of the 2017 Notes. We had a total of 508,444,280 shares of our common stock issued and outstanding, post settlement on June 13, 2016 . 6. On December 5, 2016 , our wholly owned subsidiary Seadrill UK Ltd. acquired a 10% interest that an unrelated party, HH Global Alliance Investments Limited (“HHL”) held in Seadrill Mobile Units (Nigeria) Ltd, the service company for West Capella, for a notional value of $7 million . Simultaneously HHL acquired from Seadrill UK Ltd. a 49% interest in Seadrill Nigeria Operations Limited, the service company for West Jupiter for a notional value of $7 million . The impact of these transactions was to increase Seadrill’s direct ownership interest in Seadrill Partners by $7 million , and to recognize HHL’s non-controlling interest in Seadrill Nigeria Operations Ltd of $7 million . 7. During the year ended December 31, 2016 , certain consolidated VIEs of ours withdrew bank loans and made loans to the related party Ship Finance International. These balances are presented net in the consolidated statement of cash flows. Refer to Note 22 "Long-term debt" for further information. 8. During the year ended December 31, 2017 , the Ship Finance VIEs that we consolidate declared dividends payable totaling $14 million to Ship Finance ( December 31, 2016 : $113 million ). Refer to Note 34 "Variable interest entities" for further information. 9. In August 2017, Seadrill Partners amended certain credit facilities to insulate itself from Seadrill Limited. This resulted in a $109 million repayment in respect to the $440 million secured debt facility. Refer to Note 30 "Related party transactions" for further information on related party transactions. 10. In July 2017, Sevan and Cosco agreed to defer the Sevan Developer delivery period until June 30, 2020. The contract amendment included a contract termination clause for Cosco and therefore it was deemed that Sevan had lost control of the asset and therefore derecognized the newbuild asset, which was held at $620 million , construction obligation held at $526 million , and accrued interest and other liabilities held at $19 million , resulting in a net loss on disposal of $75 million . Refer to Note 6 "(Loss)/gain on disposals" for further information.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Global settlement agreement As part of the Chapter 11 proceedings, the Debtors negotiated and announced a global settlement with various creditors, including Samsung Heavy Industries Co., Ltd. and Daewoo Shipbuilding & Marine Engineering Co., Ltd on February 26, 2018. The amendments to the RSA and Investment Agreement provided for, among other items, an agreement regarding the allowed claim of the newbuild shipyards Samsung and DSME, and an immediate cessation of all litigation and discovery efforts in relation to the plan of reorganization as well as the Debtors’ rejection and recognized termination of the newbuild contracts. The settlement agreement is contingent on confirmation of the Plan. Following the allowed claim agreement in respect of the Samsung and DSME, we have recognized a liability of $1.064 billion at December 31, 2017. Due to the Plan anticipating the rejection and termination of the newbuild contracts, we have recognized an impairment of the newbuild assets related to the West Dorado, West Draco, West Aquila and the West Libra, totaling $696 million , in the year ended December 31, 2017. West Rigel settlement agreement On April 5, 2018, we entered into a settlement and release agreement, subject to Bankruptcy Court approval, with Jurong in respect of the West Rigel whereby we agreed that the share of proceeds from the sale of the West Rigel by Jurong would be $126 million . We consider that this agreement provides additional evidence for the value of the asset held for sale at December 31, 2017, and have therefore reflected the agreed share of proceeds in the sales value of the asset held for sale at the balance sheet date.

Accounting policies (Policies)

Accounting policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The Consolidated Financial Statements are presented in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP). The amounts are presented in United States dollar ("U.S. dollar" or "US$") rounded to the nearest million, unless otherwise stated. The accompanying Consolidated Financial Statements present the financial position of Seadrill Limited, the consolidated subsidiaries and the group’s interest in associated entities. Investments in companies in which we control, or directly or indirectly holds more than 50% of the voting control are consolidated in the Consolidated Financial Statements, as well as certain variable interest entities of which we are deemed to be the primary beneficiary.
Basis of consolidation	Basis of consolidation The Consolidated Financial Statements include our assets and liabilities, our majority owned and controlled subsidiaries and certain variable interest entities, (“VIE”s) in which we are deemed to be the primary beneficiary. All intercompany balances and transactions have been eliminated on consolidation. A VIE is defined as a legal entity where either (a) the total equity at risk is not sufficient to permit the entity to finance its activities without additional subordinated support; (b) equity interest holders as a group lack either i) the power to direct the activities of the entity that most significantly impact on its economic success, ii) the obligation to absorb the expected losses of the entity, or iii) the right to receive the expected residual returns of the entity; or (c) the voting rights of some investors in the entity are not proportional to their economic interests and the activities of the entity involve or are conducted on behalf of an investor with a disproportionately small voting interest. U.S. GAAP requires a VIE to be consolidated by its primary beneficiary, being the interest holder, if any, which has both (1) the power to direct the activities of the entity which most significantly impact on the entity’s economic performance, and (2) the right to receive benefits or the obligation to absorb losses from the entity which could potentially be significant to the entity. We evaluate our subsidiaries, and any other entities in which we hold a variable interest, in order to determine whether we are the primary beneficiary of the entity, and where it is determined that we are the primary beneficiary we consolidate the entity. Investment in companies in which we exercises significant influence, but do not consolidate, are accounted for using the equity method and classified within “Investments in associated companies.” We record our share of earnings or losses from associated companies in the Consolidated Statements of Operations as “Share in results from associated companies.” The excess, if any, of purchase price over book value of our investments in equity method investees is included in the accompanying consolidated balance sheets in “Investment in associated companies.” Investments in companies in which our ownership is less than 20% are valued at fair value and classified within “Marketable Securities” unless it is not possible to estimate fair value, then the cost method is used.
Bankruptcy accounting	Bankruptcy accounting Seadrill Limited and certain of its direct and indirect consolidated subsidiaries (the “Debtors”) filed voluntary petitions on September 12, 2017 (the "Petition Date") to commence prearranged reorganization proceedings under Chapter 11 of Title 11 of the United States Bankruptcy Code (“Bankruptcy Code”) in the Southern District of Texas (the “Bankruptcy Court”) [case number 17-60079]. The Debtors also commenced a provisional liquidation proceeding in Bermuda on behalf of the Bermudian entities. During the pendency of the Chapter 11 proceedings, the Debtors will operate its business as “debtor-in-possession” under the jurisdiction of the Bankruptcy Court and in accordance with the applicable provision of the Bankruptcy Code. Read Note 3 for a discussion of the Chapter 11 proceedings. The consolidated financial statements have been prepared as if we are a going concern and reflect the application of Accounting Standards Codification 852, Reorganizations ("ASC 852") . ASC 852 requires that the financial statements, for periods subsequent to filing bankruptcy petitions, distinguish transactions and events that are directly associated with the reorganization from the ongoing operations of the business. Accordingly, certain expenses, gains and losses that are realized or incurred in the bankruptcy proceedings are recorded in “Reorganization items, net" on the Company’s Consolidated Statements of Operations. In addition, ASC 852 provides for changes in the accounting and presentation of significant items on the consolidated balance sheets, particularly liabilities. Pre-petition obligations that may be impacted by the Chapter 11 reorganization process have been classified on the consolidated balance sheets in liabilities subject to compromise. These liabilities are reported at the amounts expected to be allowed by the Bankruptcy Court, even if they may be settled for lesser amounts. If we emerge from bankruptcy, we will assess the criteria for applying fresh start accounting. If the criteria are met, we will apply fresh start accounting and record our assets and liabilities at fair value as of the fresh start reporting date. The fair value of our assets and liabilities as of that date may differ materially from the recorded values of our assets and liabilities as reflected in our historical Consolidated Financial Statements. In addition, the adoption of fresh start accounting may materially affect the results of operations following the fresh-start reporting date, as we will have a new basis in our assets and liabilities. Consequently, our historical financial statements would not be reliable indicators of our financial condition and results of operations for any period should we apply fresh start accounting.
Going Concern	Going Concern Our consolidated financial statements have been prepared on a going concern basis and contemplate the realization of assets and satisfaction of liabilities in the normal course of business. Our going concern assumption is based on management’s expectation that the current restructuring program described in Note 3 "Chapter 11 Proceedings" will alleviate the primary conditions that raise substantial doubt as to our ability to continue as a going concern when completed. Furthermore, our business operations are unaffected by the Chapter 11 Proceedings and the restructuring efforts, and we expect to meet our ongoing customer and business counterparty obligations during the course of the proceedings. We have been engaged in discussions with our banks, potential new investors, existing stakeholders and bondholders in order to restructure our secured credit facilities and unsecured liabilities and recapitalize our balance sheet with new capital. These collaborative efforts resulted in the signing of a Restructuring Support and Lock-Up Agreement (“RSA”) on September 12, 2017, subsequently amended on February 26, 2018, which provides for several conditions to be met in order to fully effectuate the intended restructuring. Although we anticipate that our restructuring plan will address our liquidity concerns, uncertainty remains over the bankruptcy court's approval of our plan of reorganization, and therefore substantial doubt exists over our ability to continue as a going concern for twelve months after the date the financial statement are issued. To the extent the Plan is confirmed, and we emerge from Chapter 11,we expect this substantial doubt to be mitigated. The consolidated financial statements do not include any adjustments that might result from the outcome of the going concern uncertainty. Upon emergence from Chapter 11 proceedings adjustments to the carrying values and classifications of our assets and liabilities and the reported amounts of income and expenses could be required that may be material. For further details of management’s plan to alleviate substantial doubt relating to going concern, refer to Note 3 "Chapter 11 Proceedings".
Use of estimates	Use of estimates Preparation of financial statements in accordance with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Contract revenue	Contract revenue A substantial majority of our revenues are derived from dayrate based drilling contracts and other service contracts. We recognize dayrate revenues ratably over the contract period when services are rendered. Under some contracts, we are entitled to additional payments for meeting or exceeding certain performance targets. Such additional payments are recognized when any contingencies are resolved or upon completion of the drilling program. We may receive lump sum fees for the mobilization of equipment and personnel or for capital additions and upgrades prior to commencement of drilling services. These up-front fees are recognized as revenue over the expected contract term. We may also receive fees for making capital upgrades during the contract. We recognize revenue for such fees over the expected remaining contract term. In some cases, we may receive lump sum fees or dayrate based fees from customers for demobilization upon completion of a drilling contract. We recognize non-contingent demobilization fees as revenue over the expected contract term. We recognize revenue for contingent demobilization fees as earned upon completion of the drilling contract. In some countries, the local government or taxing authority may assess taxes on our revenues. Such taxes may include sales taxes, use taxes, value-added taxes, gross receipts taxes and excise taxes. We generally record tax-assessed revenue transactions on a net basis.
Reimbursable revenue and expenses	Reimbursable revenue and expenses Reimbursements received for the purchases of supplies, personnel services and other services provided on behalf of and at the request of our customers in accordance with a contract or agreement are recorded as revenue. The related costs are recorded as reimbursable expenses in the same period.
Other revenues	Other revenues In a business combination there may exist unfavorable drilling contracts which are recorded at fair value at the date of acquisition. An unfavorable drilling contract is a contract that has a dayrate which differs from prevailing market rates at the time of acquisition. The net present values of such contracts are recorded as a liability at the purchase date and subsequently recognized as revenue over the contract term. Related party revenues relate to management support and administrative services provided to Seadrill Partners and SeaMex. External management fees relate to the operational, administrative and support services provided to third parties. Other revenues also include amounts recognized as early termination fees under drilling contracts which have been terminated prior to the contract end date. Contract termination fees are recognized daily as and when any contingencies or uncertainties are resolved.
Mobilization and demobilization expenses	Mobilization and demobilization expenses We incur costs to prepare a drilling unit for a new customer contract and to move the rig to the contract location. We recognize the expense for such mobilization costs over the expected contract term. We incur costs to transfer a drilling unit to a safe harbor or different geographic area at the end of a contract. We expense such demobilization costs as incurred. We also expense any costs incurred to relocate drilling units that are not under contract.
Vessel and Rig Operating expenses	Vessel and Rig Operating Expenses Vessel and rig operating expenses are costs associated with operating a drilling unit that is either in operation or stacked, and include the remuneration of offshore crews and related costs, rig supplies, insurance costs, expenses for repairs and maintenance and costs for onshore support personnel. We expense such costs as incurred.
Repairs, maintenance and periodic surveys	Repairs, maintenance and periodic surveys Costs related to periodic overhauls of drilling units are capitalized and amortized over the anticipated period between overhauls, which is generally five years. Related costs are primarily yard costs and the cost of employees directly involved in the work. We include amortization costs for periodic overhauls in depreciation and amortization expense. Costs for other repair and maintenance activities are included in vessel and rig operating expenses and are expensed as incurred.
Foreign currencies	Foreign currencies Seadrill Limited and the majority of our subsidiaries use U.S. dollars as the functional currency because the majority of our revenues and expenses are denominated in U.S. dollars. Accordingly, our reporting currency is also U.S. dollars. For subsidiaries that maintain their accounts in currencies other than U.S. dollars, we use the current method of translation whereby the Statement of Operations are translated using the average exchange rate for the year and the assets and liabilities are translated using the year-end exchange rate. Foreign currency translation gains or losses on consolidation are recorded as a separate component of other comprehensive income in shareholders' equity. Transactions in foreign currencies are translated into U.S. dollars at the rates of exchange in effect at the date of the transaction. Foreign currency assets and liabilities are translated using rates of exchange at the balance sheet date. Gains and losses on foreign currency transactions are included in the Consolidated Statements of Operations.
Current and non-current classification	Current and non-current classification Assets and liabilities (excluding deferred taxes) are classified as current assets and liabilities respectively, if their maturity is within one year of the balance sheet date. Otherwise, they are classified as non-current assets and liabilities.
Cash and cash equivalents	Cash and cash equivalents Cash and cash equivalents consist of cash, bank deposits and highly liquid financial instruments with maturities of three months or less.
Restricted cash	Restricted cash Restricted cash consists of bank deposits which have been pledged as collateral for certain guarantees issued by a bank or minimum deposits which must be maintained in accordance with contractual arrangements. Restricted cash amounts with maturities longer than one year are classified as non-current assets.
Equity method investments	Equity method investments Investments in common stock are accounted for using the equity method of accounting if the investment gives us the ability to exercise significant influence, but not control over, the investee. Significant influence is generally deemed to exist if our ownership interest in the voting stock of the investee is between 20% and 50%, although other factors such as representation on the investee’s Board of Directors and the nature of commercial arrangements are also considered. Under the equity method of accounting, we record investments in equity-method investees in the consolidated balance sheet under “Investment in associated companies” and our share of the investees’ earnings or losses together with other-than-temporary impairments in value and gain/loss on sale of investments under “Share in results from associated companies (net of tax)” in the consolidated statements of income. All other equity investments, which consist of investments that do not gives us the ability to exercise significant influence as well as investments in equity instruments other than common stock, are accounted for under the cost method or at fair value, if readily determinable. We analyze our equity method investments for impairment at each reporting period to evaluate whether an event or change in circumstances has occurred in that period that may have a significant adverse effect on the value of the investment. We record an impairment charge for other-than-temporary declines in value when the value is not anticipated to recover above the cost within a reasonable period after the measurement date, unless there are mitigating factors that indicate impairment may not be required. If an impairment charge is recorded, subsequent recoveries in value are not reflected in earnings until sale of the equity method investee occurs.
Marketable securities	Marketable securities Marketable equity securities which do not give us the ability to exercise significant influence are classified as available-for-sale. These are remeasured at fair value each reporting period with resulting unrealized gains and losses recorded as a separate component of accumulated other comprehensive income in shareholders’ equity. Gains and losses are not realized until the securities are sold or subject to an other than temporary impairment. Gains and losses on forward contracts to purchase marketable equity securities that do not meet the definition of a derivative are accounted for as available-for-sale. We analyze our available-for-sale securities for impairment at each reporting period to evaluate whether an event or change in circumstances has occurred in that period that may have a significant adverse effect on the value of the securities. We record an impairment charge for other-than-temporary declines in value when the value is not anticipated to recover above the cost within a reasonable period after the measurement date, unless there are mitigating factors that indicate impairment may not be required. If an impairment charge is recorded, subsequent recoveries in value are not reflected in earnings until sale of the securities held as available for sale occurs.
Receivables	Receivables Receivables, including accounts receivable, are recorded in the balance sheet at their nominal amount less an allowance for doubtful accounts. We establish reserves for doubtful accounts on a case-by-case basis when it is unlikely that required payments of specific amounts will occur. In establishing these reserves, we consider the financial condition of the customer as well as specific circumstances related to the receivable such as customer disputes. Receivable amounts determined as being unrecoverable are written off.
Newbuildings	Newbuildings The carrying value of drilling units under construction (“Newbuildings”) represents the accumulated costs at the balance sheet date. Cost components include payments for yard installments and variation orders, construction supervision, equipment, spare parts, capitalized interest, costs related to first time mobilization and commissioning costs. No charge for depreciation is made until commissioning of the newbuilding has been completed and it is ready for its intended use. We may have option agreements with shipyards to order new drilling units at fixed or variable prices which require some or no additional payment upon exercise. Payments for drilling unit purchase options are capitalized at the time when option contracts are acquired or entered into. We review the expected future cash flows, which would result from the exercise of each option contract on a contract by contract basis to determine whether the carrying value of the option is recoverable. Newbuildings are evaluated for impairment according to the impairment of long-lived assets accounting policy described below.
Capitalized interest	Capitalized interest Interest expense is capitalized during construction of newbuildings based on accumulated expenditures for the applicable project at our current rate of borrowing. The amount of interest expense capitalized in an accounting period shall be determined by applying an interest rate (“the capitalization rate”) to the average amount of accumulated expenditures for the asset during the period. The capitalization rates used in an accounting period shall be based on the rates applicable to borrowings outstanding during the period. We don't capitalize amounts beyond the actual interest expense incurred in the period. If our financing plans associate a specific loan with a qualifying asset, we use the rate on that loan as the capitalization rate to be applied to that portion of the average accumulated expenditures for the asset, provided that his amount does not exceed the amount of the loan. If average accumulated expenditures for the asset exceed the amounts of loans associated with the asset, the capitalization rate to be applied to such excess shall be a weighted average of the rates applicable to our other loans. During Chapter 11 no interest on newbuildings has been capitalized as interest payments made during bankruptcy proceedings are treated as adequate protection payments.
Drilling units	Drilling units Rigs, vessels and related equipment are recorded at historical cost less accumulated depreciation. The cost of these assets, less estimated residual value is depreciated on a straight-line basis over their estimated remaining economic useful lives. The estimated residual value is taken to be offset by any decommissioning costs that may be incurred. The estimated economic useful life of our floaters and, jack-up rigs, when new, is 30 years. Significant investments are capitalized and depreciated in accordance with the nature of the investment. Significant investments that are deemed to increase an asset’s value for its remaining useful life are capitalized and depreciated over the remaining life of the asset. Drilling units that are acquired in business combinations are recognized at fair value on date of acquisition. Cost of property and equipment sold or retired, with the related accumulated depreciation and write-downs are removed from the consolidated balance sheet, and resulting gains or losses are included in the consolidated statement of operations.
Assets held for sale	Assets held for sale Assets are classified as held for sale when all of the following criteria are met: Management, having the authority to approve the action, commits to a plan to sell the asset (disposal group), the asset is available for immediate sale in its present condition subject only to terms that are usual and customary for sales of such assets, an active program to locate a buyer and other actions required to complete the plan to sell the asset (disposal group) have been initiated, the sale of the asset is probable, and transfer of the asset is expected to qualify for recognition as a completed sale, within 1 year. The term probable refers to a future sale that is likely to occur, the asset is being actively marketed for sale at a price that is reasonable in relation to its current fair value and actions required to complete the plan indicate that it is unlikely that significant changes to the plan will be made or that the plan will be withdrawn.
Discontinued operations	Discontinued operations If the disposal of a component represents a strategic shift that has had (or will have) a major effect on our operations and financial results, then we present the results of that component as discontinued, provided that the component has either been disposed of or is classified as held for sale at the reporting date.
Equipment	Equipment Equipment is recorded at historical cost less accumulated depreciation and is depreciated over its estimated remaining useful life. The estimated economic useful life of equipment, when new, is between 3 and 5 years depending on the type of asset.
Other intangible assets and liabilities	Other intangible assets and liabilities Other intangible assets and liabilities are recorded at fair value on the date of acquisition less accumulated amortization. The amounts of these assets and liabilities less the estimated residual value, if any, is generally amortized on a straight-line basis over the estimated remaining economic useful life or contractual period. Other intangible assets include technology, customer relationships and favorable drilling contracts. Other intangible liabilities include unfavorable drilling contracts.
Impairment of long-lived assets	Impairment of long-lived assets We review the carrying value of our long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may no longer be appropriate. We first assess recoverability of the carrying value of the asset by estimating the undiscounted future net cash flows expected to result from the asset, including eventual disposal. If the undiscounted future net cash flows are less than the carrying value of the asset, we then compare the carrying value of the intangible asset with the discounted future net cash flows, using relevant WACC to determine an impairment loss to be recognized during the period.
Defined benefit pension plans	Defined benefit pension plans We have several defined benefit plans which provide retirement, death and early termination benefits. Our net obligation is calculated separately for each plan by estimating the amount of the future benefit that employees have earned in return for their cumulative service. The aggregated projected future benefit obligation is discounted to a present value, and the aggregated fair value of any plan assets is deducted. The discount rate is the market yield at the balance sheet date on government bonds in the relevant currency and based on terms consistent with the post-employment benefit obligations. The retirement benefits are generally a function of number of years of employment and amount of employees’ remuneration. The plans are primarily funded through payments to insurance companies. We record pension costs in the period during which the services are rendered by the employees. Actuarial gains and losses are recognized in the Statement of Operations when the net cumulative unrecognized actuarial gains or losses for each individual plan at the end of the previous reporting year exceed 10 percent of the higher of the present value of the defined benefit obligation and the fair value of plan assets at that date. These gains and losses are recognized over the expected remaining working lives of the employees participating in the plans. Otherwise, recognition of actuarial gains and losses is included in other comprehensive income. Those amounts will be subsequently recognized as a component of net periodic pension cost on the same basis as the amounts recognized in accumulated other comprehensive income. On retirement, or when an employee leaves the company, the member’s pension liability is transferred to the life insurance company administering the plan, and the pension plan no longer retains an obligation relating to the leaving member. This action is deemed to represent a settlement under U.S. GAAP, as it represents the elimination of significant risks relating to the pension obligation and related assets. Under settlement accounting U.S. GAAP requires a portion of the net unrealized actuarial gains/losses to be recognized through the Statement of Operations. The portion corresponds to the relative value of the obligation reduction as a result of the settlement. However, settlement accounting is not required if the cost of all settlements in a year is not deemed to be significant in the context of the plan. We deem the settlement not to be significant when the cost of settlements in the year is less than the sum of service cost and interest cost in the year. In this case the difference between the reduction in benefit obligation and the plan assets transferred to the life insurance company is recognized within “other comprehensive income,” rather than being recognized in the Statement of Operations.
Treasury shares	Treasury shares Treasury shares are recognized at cost as a component of equity. We record the nominal value of treasury shares purchased as a reduction in share capital. The amount paid in excess of the nominal value is treated as a reduction of additional paid-in capital.
Derivative Financial Instruments and Hedging Activities	Derivative Financial Instruments and Hedging Activities Historically, our main derivative instruments included interest-rate swap agreements, foreign currency options and forward exchange contracts which were recorded at fair value. Changes in the fair value of derivatives, which have not been designated as hedging instruments, are recorded as a gain or loss as a separate line item within "financial items" in the Consolidated Statements of Operations. Changes in the fair value of any derivative instrument that has been formally designated as a hedge, are recognized in "Accumulated other comprehensive income" in the Consolidated Balance Sheets. Any change in fair value relating to an ineffective portion of a designated hedge is recognized, in the Consolidated Statements of Operations. When the hedged item affects the income statement, the gain or loss included in Accumulated other comprehensive income is reported on the same line in the consolidated statements of operations as the hedged item.
Income taxes	Income taxes Seadrill is a Bermuda company that has subsidiaries and affiliates in various jurisdictions. Currently, Seadrill and our Bermudan subsidiaries and affiliates are not required to pay taxes in Bermuda on ordinary income or capital gains as they qualify as exempt companies. Seadrill and our subsidiaries and affiliates have received written assurance from the Minister of Finance in Bermuda that we will be exempt from taxation until March 2035. Certain subsidiaries operate in other jurisdictions where taxes are imposed. Consequently, income taxes have been recorded in these jurisdictions when appropriate. Our income tax expense is based on our income and statutory tax rates in the various jurisdictions in which we operate. We provide for income taxes based on the tax laws and rates in effect in the countries in which operations are conducted and income is earned. The determination and evaluation of our annual group income tax provision involves interpretation of tax laws in various jurisdictions in which we operate and requires significant judgment and use of estimates and assumptions regarding significant future events, such as amounts, timing and character of income, deductions and tax credits. There are certain transactions for which the ultimate tax determination is unclear due to uncertainty in the ordinary course of business. We recognize tax liabilities based on our assessment of whether our tax positions are more likely than not sustainable, based solely on the technical merits and considerations of the relevant taxing authorities widely understood administrative practices and precedence. Changes in tax laws, regulations, agreements, treaties, foreign currency exchange restrictions or our levels of operations or profitability in each jurisdiction may impact our tax liability in any given year. While our annual tax provision is based on the information available to us at the time, a number of years may elapse before the ultimate tax liabilities in certain tax jurisdictions are determined. Current income tax expense reflects an estimate of our income tax liability for the current year, withholding taxes, changes in prior year tax estimates as tax returns are filed, or from tax audit adjustments. Income tax expense consists of taxes currently payable and changes in deferred tax assets and liabilities calculated according to local tax rules. Deferred tax assets and liabilities are based on temporary differences that arise between carrying values used for financial reporting purposes and amounts used for taxation purposes of assets and liabilities and the future tax benefits of tax loss carry forwards. Our deferred tax expense or benefit represents the change in the balance of deferred tax assets or liabilities as reflected on the balance sheet. Valuation allowances are determined to reduce deferred tax assets when it is more likely than not that some portion or all of the deferred tax assets will not be realized. To determine the amount of deferred tax assets and liabilities, as well as at the Valuation allowances, we must make estimates and certain assumptions regarding future taxable income, including where our drilling units are expected to be deployed, as well as other assumptions related to our future tax position. A change in such estimates and assumptions, along with any changes in tax laws, could require us to adjust the deferred tax assets, liabilities, or valuation allowances. The amount of deferred tax provided is based upon the expected manner of settlement of the carrying amount of assets and liabilities, using tax rates enacted at the balance sheet date. The impact of tax law changes is recognized in periods when the change is enacted.
Deferred charges	Deferred charges Loan related costs, including debt issuance, arrangement fees and legal expenses, are capitalized and presented in the balance sheet as a direct deduction from the carrying amount of the related debt liability, and amortized over the term of the related loan and the amortization is included in interest expense.
Convertible debt	Convertible debt Convertible bond loans include both a loan component (host contract) and an option to convert the loan to shares (embedded derivative). An embedded derivative, such as a conversion option, may be separated from its host contract and accounted for separately if certain criteria are met (including if the contract that embodies both the embedded derivative and the host contract is not measured at fair value, the economic characteristics and risks of the embedded derivative instrument are not clearly and closely related to the economic characteristics and risks of the host contract and if a separate instrument with the same terms as the embedded instrument would be a derivative). If an embedded derivative instrument is separated from its host contract, the host contract shall be accounted for based on generally accepted accounting principles applicable to instruments of that type which do not contain embedded derivative instruments.
Total Return Equity Swaps	Total Return Equity Swaps From time to time, we enter into total return equity swaps (“TRS”) indexed to our own shares. Under such arrangements, the counterparty acquires shares in Seadrill and we carry the risk of fluctuations in the market price of those shares. The fair value of each TRS is recorded as an asset or liability, with the changes in fair value recorded in the consolidated statement of operations. We may, from time to time, enter into TRS arrangements indexed to shares in other companies which are accounted for in a similar manner.
Share-based compensation	Share-based compensation We have an employee share ownership plan under which our employees, directors and officers may be allocated options to subscribe for new shares in the ultimate parent, Seadrill Limited. The compensation cost for share options is recognized as an expense over the service period based on the fair value of the options granted. The fair value of the share options issued under employee share option plans is determined at grant date taking into account the terms and conditions upon which the options are granted, and using a valuation technique that is consistent with generally accepted valuation methodologies for pricing financial instruments, and that incorporates all factors and assumptions that knowledgeable, willing market participants would consider in determining fair value. The fair value of the share options is recognized as personnel expenses with a corresponding increase in equity over the period during which the employees become unconditionally entitled to the options. Compensation cost is initially recognized based upon options expected to vest with appropriate adjustments to reflect actual forfeitures. National insurance contributions arising from such incentive programs are expensed when the options are exercised. We also have a Restricted Stock Unit(“RSU”) plan where the holder of an award is entitled to receive shares if still employed at the end of the three -year vesting period. There is no requirement for the holder to pay for the share on grant or vesting of the award. The fair value of the RSU award is calculated as the market share price on grant date. The fair value of the awards expected to vest is recognized as compensation cost straight-line over the vesting period.
Loss contingencies	Loss contingencies We recognize a loss contingency in the consolidated balance sheet where we have a present legal or constructive obligation as a result of a past event, and it is probable that an outflow of economic benefits will be required to settle the obligation and a reliable estimate of the amount can be made. If the effect is material, provisions are determined by discounting the expected future cash flows at a pre-tax rate that reflects current market assessments of the time value of money and, where appropriate, the risks specific to the liability.
Related parties	Related parties Parties are related if one party has the ability, directly or indirectly, to control the other party or exercise significant influence over the other party in making financial and operating decisions. Parties are also related if they are subject to common control or common significant influence.
Earnings per share	Earnings per share Basic earnings per share (“EPS”) is calculated based on the income/(loss) for the period available to common stockholders divided by the weighted average number of shares outstanding for basic EPS for the period. Diluted EPS includes the effect of the assumed conversion of potentially dilutive instruments. This includes share options, restricted stock units and convertible debt. The determination of dilutive earnings per share may require us to make adjustments to net income and the weighted average shares outstanding.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards We adopted the following accounting standard updates ("ASUs") in the year, none of which had any impact on our consolidated financial statements and related disclosures: • ASU 2016-05 - Derivatives and Hedging (Topic 815): Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships (a consensus of the Emerging Issues Task Force) • ASU 2016-06 - Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the Emerging Issues Task Force) • ASU 2016-07 - Investments—Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting • ASU 2016-09 - Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting • ASU 2016-17 - Consolidation (Topic 810): Interests Held through Related Parties that are under Common Control • ASU 2016-19 - Technical Corrections and Improvements Recently Issued Accounting Standards The FASB have issued the following ASUs that we have not yet adopted but which could affect our consolidated financial statements and related disclosures in future periods. • ASU 2014-09 - Revenue from Contracts with Customers (also 2016-8, 2016-10, 2016-11, 2016-12, 2016-20, 2017-13, 2017-14) • ASU 2016-01 - Financial Instruments — Recognition and Measurement of Financial Assets and Financial Liabilities • ASU 2016-02 - Leases • ASU 2016-13 - Financial Instruments — Measurement of Credit Losses on Financial Instruments • ASU 2016-15 - Statement of Cash Flows — Classification of Certain Cash Receipts and Cash Payments • ASU 2016-16 - Income taxes — Intra-Entity Transfers of Assets other than Inventory • ASU 2016-18 - Statement of Cash Flows — Restricted Cash • ASU 2017-01 - Business Combinations — Clarifying the Definition of a Business • ASU 2017-04 - Intangibles — Simplifying the Test for Goodwill Impairment • ASU 2017-05 - Other Income—Gains and Losses from the Derecognition of Nonfinancial Assets ASU 2014-09 - Revenue from contracts with customer ASU 2014-09 - Revenue from contracts with customers In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers , which provides new authoritative guidance on the methods of revenue recognition and related disclosure requirements. This new standard supersedes all existing revenue recognition requirements, including most industry-specific guidance. We will be required to apply this standard for the year ended December 31, 2018 and for interim periods within that year. We have substantially completed our work to implement the new standard and do not expect our pattern of revenue recognition to materially change as a consequence of adopting the new guidance. We plan to use the modified retrospective method to transition to the new standard. This method requires us to apply the new standard to all outstanding contracts as of January 1, 2018. Under this method we record the cumulative effect of applying the new standard as an adjustment to opening retained earnings. To apply the standard, we were required to assess the core promise made to our customers under a drilling contract. We have assessed that our core promise is to stand ready to provide drilling services, as directed by our customer, over the operating period of a contract. We have concluded that this promise is provided as a series of distinct services that are substantially the same and have the same pattern of transfer to the customer. Therefore, we follow the so-called series guidance and treat the series of distinct services as a single performance obligation. Under the series guidance we allocate variable contract revenue to either the entire contract or individual periods during the contract, depending on what the variable contract revenue relates to. We have concluded that dayrate and bonus revenue relate to individual periods and allocate them accordingly. Mobilization and demobilization revenues don't relate to specific periods and we have concluded that they will be allocated to the entire contract, subject to the constraint around revenue reversals which is explained below. To apply the ASC 606 revenue model, we will be required to estimate the value of each component of variable contract revenue each reporting period. We will then recognize revenue equal to the estimated value of contract revenue that has been allocated to the current reporting period plus any change in the estimated value of contract revenue that has been allocated to previous reporting periods. We will generally use the most likely amount basis to form our estimates of variable contract revenue. However, if there is a range of potential outcomes for a component of variable revenue under a contract it may be appropriate to use an expected value basis instead. We only include estimates of variable contract revenue to the extent that it is probable that there will not be a significant reversal of revenue in a future reporting period. The application of this revenue model leads to a similar revenue recognition to the approach previously followed under ASC 605. However, we have identified several differences as set out below: • Under ASC 605 we recognized contingent demobilization fees as the demobilization was performed at the end of the contract. Under ASC 606 we will estimate the amount of contingent demobilization fee each reporting period and recognize the estimated fee over the expected contract term, subject to the constraint that it must be probable that this will not result in a subsequent reversal of revenue in future periods ("reversal constraint"). • Under ASC 605 we recognized disputed dayrates when the revenue became fixed or determinable. Under ASC 606 we will estimate the amount of disputed dayrate billings and recognize the estimated amount as revenue in the period the disputed dayrates related to, subject to the reversal constraint. • Under ASC 605 we recognized contingent early termination fees on daily basis over the termination period. Under ASC 606 we will estimate the amount of early termination fees for any contract that have been early terminated. We will recognize this amount as revenue at the point the contract is early terminated, subject to the reversal constraint. • Under ASC 605 we did not allocate revenue to customer options. Under ASC 606 we will assess whether a customer option provides a material right to the customer. Where a contract includes a customer option that provides a material right we will allocate a proportion of contract revenue to the material right and recognize this either at the point the option expires or when the additional services are provided. • Under ASC 605 we applied the terms of contract modifications or extensions from the point they became effective. Where a contract was extended we changed the period over which unamortized mobilization revenue was taken to income. Under ASC 606 we will account for contract modifications either as separate contracts, a single combined contract or under the cumulative catch up method, depending on the terms of the modification. As part of our implementation we have assessed our open contracts at January 1, 2018 (the "transition date"). Based on our implementation work to date we have not identified any adjustments at the transition date and do not expect material differences between our revenue under ASC 605 and ASC 606 going forward. This assessment may change as we finalize our work to implement of the new standard. ASU 2016-01 Financial Instruments - Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, which made targeted improvements to the recognition and measurement of financial assets and financial liabilities. The update changes how entities measure equity investments that do not result in consolidation and are not accounted for under the equity method and how they present changes in the fair value of financial liabilities measured under the fair value option that are attributable to their own credit. The new guidance also changes certain disclosure requirements and other aspects of current U.S. GAAP. The guidance will be effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years and early adoption is permitted in some cases. As a result of this adoption we expect to reclassify $32 million of previously recognized fair value gains from accumulated other comprehensive income to retained earnings as of January 1, 2018. ASU 2016-02 - Leases In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) . The update requires an entity to recognize right-of-use assets and lease liabilities on its balance sheet and disclose key information about leasing arrangements. It also offers specific accounting guidance for a lessee, a lessor and sale and leaseback transactions. Lessees and lessors are required to disclose qualitative and quantitative information about leasing arrangements to enable a user of the financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. The guidance will be effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years and early adoption is permitted, using a modified retrospective application. We have started to assess the impact of this standard update on our Consolidated Financial Statements and related disclosures. We have determined that our drilling contracts contain a lease component and therefore adoption of this standard will result in increased disclosure of our leasing arrangements and may affect the way the we recognize revenues associated with the lease and revenue components. Based on our work to date, we don't expect our pattern of revenue recognition to change significantly compared to current accounting standards. Additionally, we will recognize lease liabilities and corresponding right-of-use assets for leasing arrangements where we are a lessee. Unless there is a significant change in these arrangements between the date of this report and the date we adopt the standard, we expect to recognize an aggregate lease liability and right-of-use asset of between $30 million and $50 million on adoption. We have provided a summary of our commitments under operating leases at December 31, 2017 in Note 33 "Operating leases". We are consulting with other drilling companies to fully determine recognition and disclosure under the new standard. We may change our initial assessment as we complete the implementation process. ASU 2016-13 - Financial Instruments - Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which revises guidance for the accounting for credit losses on financial instruments within its scope. The new standard introduces an approach, based on expected losses, to estimate credit losses on certain types of financial instruments and modifies the impairment model for available-for-sale debt securities. The guidance will be effective for annual and interim periods beginning after December 15, 2019, with early adoption permitted only from January 1, 2019. Entities are required to apply the standard’s provisions as a cumulative-effect adjustment to retained earnings as at the beginning of the first reporting period in which the guidance is adopted. We are in the early stage of evaluating the impact of this standard update. Our customers are international oil companies, national oil companies and large independent oil companies. Our financial assets are primarily held with counter parties with high credit standing and we have historically had a low incidence of bad debt expense. Therefore, we do not currently expect this guidance to significantly affect our consolidated financial statements and related disclosures when we adopt it. ASU 2016-15 - Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payments In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments based on a consensus of the Emerging Issues Task Force (EITF) , to address the classification of certain cash receipts and cash payments on the statement of cash flows. The new guidance also clarifies how the predominance principle should be applied when cash receipts and cash payments have aspects of more than one class of cash flows. The standard will be effective for annual and interim periods beginning after December 15, 2017, with early adoption permitted. Entities are required to apply the guidance retrospectively. We are in the process of evaluating the impact of this standard update on our consolidated financial statements and related disclosures. ASU 2016-16 - Income taxes - Intra Entity Transfers of Assets other than Inventory In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Income taxes Intra-Entity Transfers of Assets other than Inventory, which requires companies to recognize the income tax effects of intercompany sales or transfers of assets, other than inventory, in the income statement as income tax expense (or benefit) in the period of sale or transfer occurs. The exception to recognizing the income tax effects of intercompany sales or transfers of assets remains in place for intercompany inventory sales and transfers, i.e. companies will still be required to defer the income tax effects of intercompany inventory transactions. The standard will be effective for annual periods beginning after 15 December 2017, with early adoption permitted. Entities are required to apply the guidance on a modified retrospective basis, with the cumulative effect adjustment to retained earnings at the beginning of the period of adoption. As a result of the modified retrospective application, we will reduce "other current assets" in our Consolidated Balance Sheet with a cumulative adjustment to retained earnings of approximately $84 million as of January 1, 2018. ASU 2016-18 - Statement of Cash Flows - Restricted Cash In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash , to address classification of activity related to restricted cash and restricted cash equivalents in the cash flows. The standard eliminates the presentation of transfers between cash and cash equivalents and restricted cash and restricted cash equivalents in the statement of cash flows. When cash, cash equivalents and restricted cash equivalents are presented in more than one line item on the balance sheet, a reconciliation of the totals in the cash flows to the related captions in the balance sheet are required, either on the face of the cash flow or in the notes to the Consolidated Financial Statements. Additional disclosures are required for the nature of the restricted cash and restricted cash equivalents. The standard will be effective for fiscal years beginning after 15 December 2017, and interim periods within those years. The result of this adoption would be a classification adjustment on our prospective Consolidated Statement of Cash Flows. The total restricted cash presented on the Consolidated Balance Sheet as at December 31, 2017 was $104 million (December 31, 2016: $75 million ). ASU 2017-01 - Business Combinations - Clarifying the Definition of a Business In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business, which clarifies the definition of a business to assist entities with evaluating whether transactions should bee accounted for as acquisitions (or disposals) or assets or businesses. The guidance will be effective for annual and interim periods beginning after December 15, 2017. Entities apply the guidance prospectively. We will apply this standard when we next undertake a business acquisition or disposal. ASU 2017-04 - Intangible - Simplifying the Test for Goodwill Impairment In January 2017, the FASB issued ASU 2017-04, Intangibles — Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under the new guidance, entities will continue to perform Step 1 of the goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. The entity will now recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. We do not currently have any goodwill balances. Therefore, we do not currently expect this guidance to significantly affect our consolidated financial statements and related disclosures when we adopt it. ASU 2017-05 - Other Income—Gains and Losses from the Derecognition of Non-financial Assets In February 2017, the FASB issued 2017-05, Other Income — Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Non-financial Assets. The standard update clarifies that a model consistent with ASC 606 and ASC 810 should be applied to sales of non-financial assets to non-customers. Under this guidance an entity would recognize a gain or loss in full when it transfers control of the asset. The effective date of the guidance will be effective for annual and interim periods beginning after December 15, 2017. The new guidance is consistent with our current practice and therefore the we do not expect this guidance to affect our consolidated financial statements and related disclosures when the we adopt it. Other accounting standard updates issued by the FASB As of April 12, 2018 , the FASB have issued several further updates not included above. We do not currently expect any of these updates to affect our consolidated financial statements and related disclosures either on transition or in future periods.

Chapter 11 Proceedings (Tables)

Chapter 11 Proceedings (Tables)	12 Months Ended
	Dec. 31, 2017
Reorganizations [Abstract]
Schedule of Liabilities Subject to Compromise	Liabilities subject to compromise include the following: (In US$ millions) December 31, 2017 Senior undersecured or impaired external debt 5,371 Unsecured bonds 2,334 Derivatives previously recorded at fair value 249 Loss on Newbuilding global settlement agreement 1,064 Accounts payable and other liabilities 103 Accrued interest payable 50 Amount due to related party 20 Liabilities subject to compromise 9,191
Schedule of Reorganization Items	The following table summarizes reorganization items: (In US$ millions) December 31, 2017 Advisory and professional fees (66 ) New investor commitment fees (53 ) Unamortized debt issuance costs (66 ) Gain or loss on pre-petition allowable claims (3 ) Loss on Newbuilding global settlement agreement (1,064 ) Interest income on surplus cash invested 4 Reversal of issuing entities credit risk on derivatives (89 ) Reorganization items, net (1,337 )
Debtor-in-Possession Financing, Condensed Balance Sheet	Debtors' Condensed Combined Balance Sheet (in US$ millions) as at December 31, 2017 2017 ASSETS Cash and cash equivalents 1,157 Restricted cash 81 Marketable securities 124 Accounts receivables, net 291 Amount due from related parties - current 213 Intra group receivables 1,064 Other current assets 257 Total current assets 3,187 Non-current assets Investment in associated companies 1,346 Drilling units 12,568 Shares in subsidiaries 6,501 Deferred tax assets 10 Equipment 29 Amount due from related parties - non-current 547 Intra group non-current assets 475 Other non-current assets 81 Total non-current assets 21,557 Total assets 24,744 LIABILITIES AND EQUITY Current liabilities Trade accounts payable 69 Amounts due to related parties - current 6 Intra group liabilities 961 Other current liabilities 240 Total current liabilities 1,276 Liabilities subject to compromise 9,191 Non-current liabilities Deferred tax liabilities 108 Intra group non-current liabilities 1,434 Other non-current liabilities 69 Total non-current liabilities 1,611 Total equity 12,666 Total liabilities and equity 24,744
Debtor-in-Possession Financing, Condensed Income Statement	Debtors' Condensed Combined Statement of Operations (in US$ millions) for the period of September 12, 2017 to December 31, 2017 2017 Operating revenues Contract revenues 463 Reimbursable revenues 12 Intra group revenues 27 Other revenues 1 Total operating revenues 503 Loss on disposals (95 ) Contingent consideration realized 9 Operating expenses Vessel and rig operating expenses (262 ) Reimbursable expenses (11 ) Depreciation and amortization (229 ) Intra group expenses (16 ) Loss on impairment of long lived assets (696 ) Total operating expenses (1,214 ) Operating loss (797 ) Financial items and other income/(expense), net Interest income/(expense), net 21 Share in results from associated companies (net of tax) 67 Loss on impairment of investments (841 ) Loss on derivative financial instruments (2 ) Foreign exchange gain 8 Reorganization Items, net (1,337 ) Other financial items and other income, net 8 Total financial items and other expense, net (2,076 ) Loss before income taxes (2,873 ) Income tax expense (67 ) Net loss (2,940 ) Net loss attributable to the non-controlling interest (67 ) Net loss attributable to the parent (2,873 )
Debtor-in-Possession Financing, Condensed Cash Flow Statement	Debtors' Condensed Combined Statement of Cash Flows (in US$ millions) for the period of September 12, 2017 to December 31, 2017 2017 Cash Flows from Operating Activities Net cash provided by operating activities 294 Cash Flows from Investing Activities Additions to newbuildings (1 ) Additions to drilling units and equipment (20 ) Contingent consideration received 28 Change in restricted cash (10 ) Proceed from repayment of short term loan to related parties 8 Net cash provided by investing activities 5 Cash Flows from Financing Activities Repayments of debt (77 ) Debt fees paid (53 ) Net cash used in financing activities (130 ) Effect of exchange rate changes on cash and cash equivalents (2 ) Net increase in cash and cash equivalents 167 Cash and cash equivalents at beginning of the year 990 Cash and cash equivalents at the end of year 1,157

Segment information (Tables)

Segment information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Results	Revenues Year ended December 31, (In US$ millions) 2017 2016 2015 Floaters 1,387 2,212 2,906 Jack-up rigs 617 865 1,293 Other 84 92 136 Total 2,088 3,169 4,335 Depreciation and amortization Year ended December 31, (In US$ millions) 2017 2016 2015 Floaters 601 600 570 Jack-up rigs 197 210 208 Other — — 1 Total 798 810 779 Operating income – net income Year ended December 31, (In US$ millions) 2017 2016 2015 Floaters (622 ) 759 340 Jack-up Rigs (112 ) 267 664 Other 6 — 15 Operating income (728 ) 1,026 1,019 Unallocated items: Total financial items and other (2,308 ) (982 ) (1,446 ) (Loss)/income before income taxes (3,036 ) 44 (427 ) Drilling Units and Newbuildings - Total assets (In US$ millions) December 31, 2017 December 31, 2016 Floaters 9,956 11,751 Jack-up Rigs 3,508 4,056 Total Drilling Units and Newbuildings 13,464 15,807 Assets held for sale 126 128 Investments in Associated companies 1,473 2,168 Marketable securities 124 110 Cash and restricted cash 1,359 1,443 Other assets 1,436 2,010 Total 17,982 21,666 Capital expenditures – fixed assets Year ended December 31, (In US$ millions) 2017 2016 2015 Floaters 128 192 950 Jack-up Rigs 22 35 95 Total 150 227 1,045
Company's Revenues and Fixed Assets by Geographic Area	Fixed assets – drilling units (1) (In US$ millions) December 31, 2017 December 31, 2016 Norway 2,258 2,456 Spain 2,016 944 Brazil 1,816 1,884 Malaysia 1,809 673 USA 1,266 1,298 Others (2) 4,051 5,598 Total 13,216 12,853 (1) The fixed assets referred to in the table above exclude assets under construction. Asset locations at the end of a period are not necessarily indicative of the geographic distribution of the revenues or operating profits generated by such assets during such period. (2) Other countries represent countries in which we operate that individually had fixed assets representing less than 10% of total fixed assets for any of the periods presented. Geographic segment data Revenues are attributed to geographical segments based on the country of operations for drilling activities, i.e. the country where the revenues are generated. The following presents our revenues and fixed assets by geographic area: Revenues Year ended December 31, (In US$ millions) 2017 2016 2015 Angola 482 419 527 Brazil 358 491 877 United States 291 370 371 Norway 219 475 641 Nigeria 193 431 499 Others (1) 545 983 1,420 Total Revenue 2,088 3,169 4,335 (1) Other countries represent countries in which we operate that individually had revenues representing less than 10% of total revenues earned for any of the periods presented.
Major Customers	In the years ended December 31, 2017 , 2016 and 2015 , we had the following customers with contract revenues greater than 10% in any of the years presented: Year ended December 31, 2017 2016 2015 Total S.A Group ("Total") 25 % 18 % 16 % Petroleo Brasileiro S.A ("Petrobras") 19 % 17 % 19 % LLOG 15 % 13 % 9 % Exxon Mobil Corp ("Exxon") 7 % 13 % 14 % Statoil ASA ("Statoil") 4 % 10 % 12 %

Other revenues (Tables)

Other revenues (Tables)	12 Months Ended
	Dec. 31, 2017
Revenues [Abstract]
Other revenues	Other revenues consist of the following: Year ended December 31, (In US$ millions) 2017 2016 2015 Revenues related party 110 100 119 Amortization of unfavorable contracts 43 65 116 External management fees with third parties 1 19 30 Termination revenue 8 69 — Total 162 253 265

Loss on disposals (Tables)

Loss on disposals (Tables)	12 Months Ended
	Dec. 31, 2017
Proceeds from Sale of Productive Assets [Abstract]
Disposals	have recognized the following (losses)/gains on disposals: (In US$ millions) Net proceeds/recoverable amount Book value on disposal (Loss)/gain Year ended December 31, 2017: Sale of West Triton 75 109 (34 ) Sale of West Mischief 75 146 (71 ) Sale of West Resolute 75 136 (61 ) Disposal of Sevan Developer contract — 75 (75 ) Sale of West Rigel 126 128 (2 ) Other — 2 (2 ) Total for year ended December 31, 2017 351 596 (245 ) Year ended December 31, 2016: Total for year ended December 31, 2016 — — — Year ended December 31, 2015: Cancellation of West Mira 199 279 (80 ) Sale of West Polaris 235 312 (77 ) SeaMex Limited 1,240 1,059 181 West Rigel transferred to Asset held for sale 128 210 (82 ) Other — 5 (5 ) Total for year ended December 31, 2015 1,802 1,865 (63 ) we have recognized the following contingent considerations: Year Ended December 31, (In US$ millions) 2017 2016 2015 West Polaris earn out realized 13 8 32 West Vela earn out realized 14 13 15 Total contingent consideration recognized 27 21 47 (In US$ millions) As at March 10, 2015 Fair value of consideration received Net cash consideration received 749 Seller’s credit recognized 250 Direct repayment of debt by the JV on behalf of Seadrill 150 Consideration receivable in respect of West Titania 162 Other related party balances payable (71 ) Cash paid to acquire 50% interest in the JV (163 ) Fair value of consideration received 1,077 Fair value of retained 50% investment in Seamex Limited 163 Carrying value of net assets Current assets Cash and cash equivalents 40 Deferred tax assets - short term 8 Other current assets 20 Total current assets 68 Non-current assets Drilling units 969 Deferred tax asset - long term 4 Other non-current assets 86 Goodwill 49 Total non-current assets 1,108 Total assets 1,176 Liabilities Current liabilities Trade accounts payable (1 ) Other current liabilities (56 ) Total current liabilities (57 ) Non-current liabilities Other non-current liabilities (60 ) Total non-current liabilities (60 ) Total liabilities (117 ) Carrying value of net assets 1,059 Gain on disposal 181 As at June 19, 2015 Initial enterprise value 540 Less: Debt assumed (336 ) Initial purchase price 204 Plus: Working capital adjustment 31 Adjusted initial purchase price 235 Cash 204 Plus: Working capital receivable 31 Fair value of purchase consideration recognized on disposal 235 Less: net carrying value of assets and liabilities (271 ) Less: allocated goodwill to subsidiaries (41 ) Loss on disposal (77 )

Interest expense (Tables)

Interest expense (Tables)	12 Months Ended
	Dec. 31, 2017
Interest Expense [Abstract]
Net interest expense	Year ended December 31, (In US$ millions) 2017 2016 2015 Gross interest expense 313 451 475 Capitalized interest (28 ) (39 ) (60 ) Interest expense 285 412 415

Impairment loss on marketable51

Impairment loss on marketable securities and investments in associated companies (Tables)	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	The table below summarizes the total impairments of investments during the years ending December 31, 2017 , 2016 and 2015 : Year ended December 31, (In US$ millions) 2017 2016 2015 Impairments of Marketable securities (refer to Note 13) Seadrill Partners - Common Units — 153 574 SapuraKencana — — 178 Total impairment of marketable securities investments (reclassification from OCI) — 153 752 Impairments of Investment in associated companies and joint ventures (refer to Note 16) Seadrill Partners - Total direct ownership investments 723 400 302 Seadrill Partners - Subordinated units 82 180 125 Seadrill Partners - Seadrill member interest and IDRs — 73 106 SeaMex Limited 36 76 — Itaunas Drilling, Camburi Drilling, and Sahy Drilling — 13 — Total impairment of investments in associated companies and joint ventures 841 742 533 Total impairment of investments 841 895 1,285 At the year end the share of recorded equity in the statutory accounts of our associated companies were as follows: (In US$ millions) December 31, 2017 December 31, 2016 December 31, 2015 Archer (1) N/A 15 79 Seabras Sapura Participacoes 63 47 24 Seabras Sapura Holding 143 77 19 Seadrill Partners (2) N/A N/A N/A Seamex 221 218 200 Total 427 357 322 (1) In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized as an available-for-sale security. (2) We account for our direct interests in operating subsidiaries of Seadrill Partners, and our ownership of Seadrill Partners Subordinated Units, under the equity method. Our share of Seadrill Partners recorded equity consists of the equity attributable to non-controlling interests in Seadrill Partners, and additionally a proportionate share of equity attributable to Seadrill Partners’ unitholders. The equity attributable to non-controlling interest in Seadrill Partners as at December 31, 2017 was $1,398 million (December 31, 2016: $1,343 million ). Seadrill’s holding in the subordinated units represents 18.0% of the limited partner interests in Seadrill Partners. Total equity attributable to Seadrill Partners' unitholders as at December 31, 2017 was $1,304 million (December 31, 2016: $1,193 million ). At year-end the book values of our investment in associated companies are as follows: (In US$ millions) December 31, 2017 December 31, 2016 Archer (1) N/A — Seabras Sapura Participacoes 63 47 Seabras Sapura Holding 290 227 Itaunas Drilling — — Camburi Drilling — — Sahy Drilling — — Seadrill Partners - Total direct ownership interests 857 1,537 Seadrill Partners - Subordinated units 97 157 Seadrill Partners - Seadrill member interest and IDRs (2) 64 64 Seamex Ltd. 102 136 Total 1,473 2,168 (1) In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized it as an available-for-sale security. (2) The Seadrill Partners - Seadrill member interest and Incentive Distribution Rights (“IDR’s”) are accounted for as cost-method investments on the basis that they do not represent common stock interests and their fair value is not readily determinable. The investments are held at cost and not subsequently re-measured. For more details on the deconsolidation of Seadrill Partners see Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information.

Taxation (Tables)

Taxation (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components of Income Taxes	Income taxes consist of the following: Year ended December 31, (In US$ millions) 2017 2016 2015 Current tax expense: Bermuda — — — Foreign 56 151 177 Deferred tax expense: Bermuda — — — Foreign 10 48 31 Total tax expense 66 199 208 Effective tax rate (2.2 )% 452.3 % (48.7 )%
Income Tax Reconciliation	The income taxes for the years ended December 31, 2017 , 2016 and 2015 differed from the amount computed by applying the Bermudan statutory income tax rate of 0% as follows: Year ended December 31. (In US$ millions) 2017 2016 2015 Income taxes at statutory rate — — — Effect of change on uncertain tax positions relating to prior year (5 ) 28 — Effect of unremitted earnings of subsidiaries 3 (4 ) 38 Effect of taxable income in various countries 68 175 170 Total tax expense 66 199 208
Net Deferred Tax Assets (Liabilities)	Deferred income taxes reflect the impact of temporary differences between the amount of assets and liabilities recognized for financial reporting purposes and such amounts recognized for tax purposes. The net deferred tax assets/(liabilities) consist of the following: Deferred tax assets: (In US$ millions) December 31, December 31, Pensions and stock options 4 3 Provisions 49 28 Net operating losses carried forward 255 272 Other — 2 Gross deferred tax assets 308 305 Valuation allowance (230 ) (245 ) Deferred tax assets, net of valuation allowance 78 60 Deferred tax liabilities: (In US$ millions) December 31, December 31, Property, plant and equipment 138 126 Unremitted Earnings of Subsidiaries 37 34 Gross deferred tax liabilities 175 160 Net deferred tax (liability)/asset (97 ) (100 )
Changes to Liabilities Related to Unrecognized Tax Benefits	The changes to our uncertain tax positions were as follows: Year ended December 31, (In US$ millions) 2017 2016 2015 Balance at the beginning of the period 44 9 9 Increases as a result of positions taken in prior periods 23 35 — Increases as a result of positions taken during the current period — 2 — Decreases as a result of positions taken in prior periods (9 ) (2 ) — Decreases as a result of positions taken in the current period — — — Decreases due to settlements (3 ) — — Balance at the end of the period 55 44 9
Earliest Tax Years that Remain Subject to Examination by Major Taxable Jurisdictions	Jurisdiction Earliest Open Year Angola 2015 Nigeria 2014 United States 2014 Norway 2013 Brazil 2008

Loss per share (Tables)

Loss per share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	The components of the numerator for the calculation of basic and diluted EPS are as follows: (In US$ millions) 2017 2016 2015 Net loss attributable to the parent (2,973 ) (181 ) (634 ) Less: Allocation to participating securities — — — Net loss available to stockholders (2,973 ) (181 ) (634 ) Effect of dilution — — — Diluted net loss available to stockholders (2,973 ) (181 ) (634 ) The components of the denominator for the calculation of basic and diluted EPS are as follows: (In US$ millions) 2017 2016 2015 Basic earnings per share: Weighted average number of common shares outstanding 505 501 493 Diluted earnings per share: Effect of dilutive convertible bonds — — — Effect of dilutive share options (1) — — — Weighted average number of common shares outstanding adjusted for the effects of dilution 505 501 493 (1) Certain stock options have been excluded from the calculation of diluted EPS because their exercise price exceeded our average share price during the calculation period. (In US$) 2017 2016 2015 Basic loss per share (5.89 ) (0.36 ) (1.29 ) Diluted loss per share (5.89 ) (0.36 ) (1.29 )

Disposals of businesses and d54

Disposals of businesses and deconsolidation of subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Calculation of Gain (Loss) on Disposal	have recognized the following (losses)/gains on disposals: (In US$ millions) Net proceeds/recoverable amount Book value on disposal (Loss)/gain Year ended December 31, 2017: Sale of West Triton 75 109 (34 ) Sale of West Mischief 75 146 (71 ) Sale of West Resolute 75 136 (61 ) Disposal of Sevan Developer contract — 75 (75 ) Sale of West Rigel 126 128 (2 ) Other — 2 (2 ) Total for year ended December 31, 2017 351 596 (245 ) Year ended December 31, 2016: Total for year ended December 31, 2016 — — — Year ended December 31, 2015: Cancellation of West Mira 199 279 (80 ) Sale of West Polaris 235 312 (77 ) SeaMex Limited 1,240 1,059 181 West Rigel transferred to Asset held for sale 128 210 (82 ) Other — 5 (5 ) Total for year ended December 31, 2015 1,802 1,865 (63 ) we have recognized the following contingent considerations: Year Ended December 31, (In US$ millions) 2017 2016 2015 West Polaris earn out realized 13 8 32 West Vela earn out realized 14 13 15 Total contingent consideration recognized 27 21 47 (In US$ millions) As at March 10, 2015 Fair value of consideration received Net cash consideration received 749 Seller’s credit recognized 250 Direct repayment of debt by the JV on behalf of Seadrill 150 Consideration receivable in respect of West Titania 162 Other related party balances payable (71 ) Cash paid to acquire 50% interest in the JV (163 ) Fair value of consideration received 1,077 Fair value of retained 50% investment in Seamex Limited 163 Carrying value of net assets Current assets Cash and cash equivalents 40 Deferred tax assets - short term 8 Other current assets 20 Total current assets 68 Non-current assets Drilling units 969 Deferred tax asset - long term 4 Other non-current assets 86 Goodwill 49 Total non-current assets 1,108 Total assets 1,176 Liabilities Current liabilities Trade accounts payable (1 ) Other current liabilities (56 ) Total current liabilities (57 ) Non-current liabilities Other non-current liabilities (60 ) Total non-current liabilities (60 ) Total liabilities (117 ) Carrying value of net assets 1,059 Gain on disposal 181 As at June 19, 2015 Initial enterprise value 540 Less: Debt assumed (336 ) Initial purchase price 204 Plus: Working capital adjustment 31 Adjusted initial purchase price 235 Cash 204 Plus: Working capital receivable 31 Fair value of purchase consideration recognized on disposal 235 Less: net carrying value of assets and liabilities (271 ) Less: allocated goodwill to subsidiaries (41 ) Loss on disposal (77 )

Restricted cash (Tables)

Restricted cash (Tables)	12 Months Ended
	Dec. 31, 2017
Restricted Cash and Investments [Abstract]
Restricted Cash	Restricted cash includes: (In US$ millions) December 31, 2017 December 31, 2016 Danske guarantee agreement 70 70 Cash pledged as collateral 6 — Tax withholding deposits 5 5 Other 23 — Short-term restricted cash 104 75 Long-term restricted cash — — Total restricted cash 104 75

Marketable securities (Tables)

Marketable securities (Tables)	12 Months Ended
	Dec. 31, 2017
Marketable Securities [Abstract]
Marketable Securities Held	The following tables summarize the carrying values of the marketable securities in the Consolidated Balance Sheet: As at December 31, 2017 (In US$ millions) Amortized Cumulative unrealized fair value gains Carrying Archer — 28 28 Seadrill Partners - Common Units 93 3 96 Total 93 31 124 As at December 31, 2016 (In US$ millions) Amortized Cumulative unrealized fair value gains Carrying Seadrill Partners - Common Units 93 17 110 Total 93 17 110
Gross Realized Gains and Losses Related to Marketable Securities	The following table summarizes the gross realized gains and losses from marketable securities during the years presented: Year ended December 31, 2017 (In US$ millions) Gross realized gains Gross realized losses Gross unrealized gains Gross unrealized losses Gross proceeds from sales Recognition and purchases Gain/(loss) reclassified into income Archer — — 42 (14 ) — — — Seadrill Partners - Common Units — — 8 (22 ) — — — Total — — 50 (36 ) — — — Year ended December 31, 2016 (In US$ millions) Gross realized gains Gross realized losses Gross unrealized gains Gross unrealized losses Gross proceeds from sales Recognition and purchases Loss reclassified into income Sapura Kencana — — — — 195 — — Seadrill Partners - Common Units — — 69 (52 ) — — (153 ) Total — — 69 (52 ) 195 — (153 ) Year ended December 31, 2015 (In US$ millions) Gross realized gains Gross realized losses Gross unrealized gains Gross unrealized losses Gross proceeds from sales Recognition and purchases Loss reclassified into income Sapura Kencana — — — (130 ) — — (178 ) Seadrill Partners - Common Units — — 16 (346 ) — — (574 ) Total — — 16 (476 ) — — (752 )

Other current assets (Tables)

Other current assets (Tables)	12 Months Ended
	Dec. 31, 2017
Other Assets [Abstract]
Other Current Assets	Other current assets include: (In US$ millions) December 31, 2017 December 31, 2016 Prepaid expenses 87 21 Deferred consideration (1) 80 135 Taxes receivable 24 25 Reimbursable amounts due from customers 15 21 Deferred mobilization cost 15 35 Receivable from ship-yard (2) — 170 Other current assets 36 88 Total other current assets 257 495 (1) On April 30, 2013, we completed the disposal of the tender rig business to SapuraKencana. The total consideration consisted of a non-contingent deferred consideration of $145 million , bearing interest at LIBOR plus 5% , which was due in April 2016 . During the year ended December 31, 2016, SapuraKencana repaid $10 million of the principal and paid $25 million of interest. On August 28, 2017 this was converted into a formalized loan agreement whereby $5 million is repaid each month, with the residual due to be repaid on August 3, 2018. We expect the entire amount will be recoverable. (2) The receivable from shipyard relates to the West Mira , which reached settlement for $170 million on March 13, 2017. For details on the arbitration process and subsequent settlement, refer to Note 6 " Loss on disposals " for more information.

Investment in associated comp58

Investment in associated companies (Tables)	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Ownership Percentages Equity Method Investments	We have the following investments that are or have been recorded using the equity method for the periods presented in these Consolidated Financial Statements: Ownership percentage December 31, 2017 December 31, 2016 December 31, 2015 Archer Limited ("Archer") Note 1 39.7 % 39.9 % Seabras Sapura Participacoes Ltda ("Seabras Sapura Participacoes") 50.0 % 50.0 % 50.0 % Seabras Sapura Holding GmbH ("Seabras Sapura Holding") 50.0 % 50.0 % 50.0 % Itaunas Drilling B.V. ("Itaunas Drilling") 30.0 % 30.0 % 30.0 % Camburi Drilling B.V. ("Camburi Drilling") 30.0 % 30.0 % 30.0 % Sahy Drilling B.V. ("Sahy Drilling") 30.0 % 30.0 % 30.0 % Seadrill Partners ("SDLP") Note 2 Note 2 Note 2 SeaMex Ltd. ("SeaMex") 50.0 % 50.0 % 50.0 % (1) As part of their financial restructuring, Archer completed two share issuances in March and April 2017, which diluted Seadrill's ownership interest to 15.7% as at December 31, 2017 . In April 2017, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized it as an available-for-sale security. (2) As at the deconsolidation date of Seadrill Partners on January 2, 2014, we recognized our ownership interests in Seadrill Partners and direct ownership interests in Seadrill Partners subsidiaries, at fair value at the date of deconsolidation. Refer to the Seadrill Partners paragraph below for additional information.
Equity Method Investments	The table below summarizes the total impairments of investments during the years ending December 31, 2017 , 2016 and 2015 : Year ended December 31, (In US$ millions) 2017 2016 2015 Impairments of Marketable securities (refer to Note 13) Seadrill Partners - Common Units — 153 574 SapuraKencana — — 178 Total impairment of marketable securities investments (reclassification from OCI) — 153 752 Impairments of Investment in associated companies and joint ventures (refer to Note 16) Seadrill Partners - Total direct ownership investments 723 400 302 Seadrill Partners - Subordinated units 82 180 125 Seadrill Partners - Seadrill member interest and IDRs — 73 106 SeaMex Limited 36 76 — Itaunas Drilling, Camburi Drilling, and Sahy Drilling — 13 — Total impairment of investments in associated companies and joint ventures 841 742 533 Total impairment of investments 841 895 1,285 At the year end the share of recorded equity in the statutory accounts of our associated companies were as follows: (In US$ millions) December 31, 2017 December 31, 2016 December 31, 2015 Archer (1) N/A 15 79 Seabras Sapura Participacoes 63 47 24 Seabras Sapura Holding 143 77 19 Seadrill Partners (2) N/A N/A N/A Seamex 221 218 200 Total 427 357 322 (1) In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized as an available-for-sale security. (2) We account for our direct interests in operating subsidiaries of Seadrill Partners, and our ownership of Seadrill Partners Subordinated Units, under the equity method. Our share of Seadrill Partners recorded equity consists of the equity attributable to non-controlling interests in Seadrill Partners, and additionally a proportionate share of equity attributable to Seadrill Partners’ unitholders. The equity attributable to non-controlling interest in Seadrill Partners as at December 31, 2017 was $1,398 million (December 31, 2016: $1,343 million ). Seadrill’s holding in the subordinated units represents 18.0% of the limited partner interests in Seadrill Partners. Total equity attributable to Seadrill Partners' unitholders as at December 31, 2017 was $1,304 million (December 31, 2016: $1,193 million ). At year-end the book values of our investment in associated companies are as follows: (In US$ millions) December 31, 2017 December 31, 2016 Archer (1) N/A — Seabras Sapura Participacoes 63 47 Seabras Sapura Holding 290 227 Itaunas Drilling — — Camburi Drilling — — Sahy Drilling — — Seadrill Partners - Total direct ownership interests 857 1,537 Seadrill Partners - Subordinated units 97 157 Seadrill Partners - Seadrill member interest and IDRs (2) 64 64 Seamex Ltd. 102 136 Total 1,473 2,168 (1) In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized it as an available-for-sale security. (2) The Seadrill Partners - Seadrill member interest and Incentive Distribution Rights (“IDR’s”) are accounted for as cost-method investments on the basis that they do not represent common stock interests and their fair value is not readily determinable. The investments are held at cost and not subsequently re-measured. For more details on the deconsolidation of Seadrill Partners see Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information.
Summarized Balance Sheet Information of Equity Method Investees	Summarized Consolidated Balance Sheet information of our equity method investees is as follows: Balance at December 31, 2017 (In US$ millions) Current assets Non-current assets Current liabilities Non-current liabilities Non-Controlling interest Archer N/A N/A N/A N/A N/A Seabras Sapura Participacoes 126 299 131 169 — Seabras Sapura Holding 341 1,331 542 845 — Seadrill Partners 1,214 5,317 546 3,284 1,398 SeaMex 294 1,036 222 666 — Total 1,975 7,983 1,441 4,964 1,398 Balance at December 31, 2016 (In US$ millions) Current assets Non-current assets Current liabilities Non-current liabilities Non-Controlling interest Archer 287 773 313 718 — Seabras Sapura Participacoes 100 317 149 174 — Seabras Sapura Holding 258 1,393 509 988 — Seadrill Partners 1,214 5,567 665 3,580 1,343 SeaMex 296 1,095 145 818 — Total 2,155 9,145 1,781 6,278 1,343
Summarized Statement of Operations Information of Equity Method Investees	Summarized Consolidated Statement of Operations information for our equity method investees is as follows: Year ended December 31, 2017 (In US$ millions) Operating revenues Net operating income Net income Net income attributable to non-controlling interest Archer N/A N/A N/A — Seabras Sapura Participacoes 76 60 34 — Seabras Sapura Holding 186 184 126 — Seadrill Partners 1,128 464 235 94 SeaMex 239 80 15 — Total 1,629 788 410 94 Year ended December 31, 2016 (In US$ millions) Operating revenues Net operating (loss)/income Net (loss)/income Net income attributable to non-controlling interest Archer 818 (41 ) (166 ) — Seabras Sapura Participacoes 148 46 39 — Seabras Sapura Holding 241 155 89 — Seadrill Partners 1,600 818 546 265 SeaMex 280 119 36 — Total 3,087 1,097 544 265 Year ended December 31, 2015 (In US$ millions) Operating revenues Net operating (loss)/income Net (loss)/income Net income attributable to non-controlling interest Archer 1,321 (13 ) (359 ) — Seabras Sapura Participacoes 53 3 1 — Seabras Sapura Holding 124 76 51 — Seadrill Partners 1,742 844 488 231 Seamex 238 79 24 — Total 3,478 989 205 231

Newbuildings (Tables)

Newbuildings (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Newbuildings	(In US$ millions) December 31, 2017 December 31, 2016 Opening balance 1,531 1,479 Additions 5 12 Capitalized interest and loan related costs 28 40 Disposals (1) (620 ) — Impairment (2) (696 ) — Closing balance 248 1,531 (1) In July 2017, Sevan Drilling and Cosco reached agreement to defer the Sevan Developer delivery period until June 30, 2020. The contract amendment included a termination clause for Cosco and therefore it was deemed that Sevan had lost control of the asset. The Newbuild asset and corresponding construction obligation were derecognized. Refer to Note 6 - Loss on disposals for further information.

Drilling units (Tables)

Drilling units (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Drilling Units	(In US$ millions) December 31, 2017 December 31, 2016 Cost 17,335 17,753 Accumulated depreciation (1) (4,119 ) (3,477 ) Net book value 13,216 14,276

Equipment (Tables)

Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Equipment	Equipment consists of office equipment, software, furniture and fittings. (In US$ millions) December 31, 2017 December 31, 2016 Cost 84 77 Accumulated depreciation (1) (55 ) (36 ) Net book value 29 41

Goodwill and other intangible62

Goodwill and other intangible assets and liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Other Intangible Assets	The gross carrying amounts and accumulated amortization were as follows: December 31, 2017 December 31, 2016 (In US$ millions) Gross carrying amount Accumulated amortization Net carrying amount Gross carrying amount Accumulated amortization Net carrying amount Unfavorable contracts - intangible liabilities Balance at the beginning of the period 444 (378 ) 66 444 (313 ) 131 Amortization of unfavorable contracts — (43 ) (43 ) — (65 ) (65 ) Balance at the end of the period 444 (421 ) 23 444 (378 ) 66
Finite-Lived Intangible Liabilities, Future Amortization Expense	The table below shows the amounts relating to unfavorable contracts that is expected to be amortized over the next five years: Year ended December 31, (In US$ millions) 2018 2019 2020 2021 2022 Total Amortization of unfavorable contracts 23 — — — — 23

Other non-current assets (Table

Other non-current assets (Tables)	12 Months Ended
	Dec. 31, 2017
Other Assets, Noncurrent Disclosure [Abstract]
Other Non-current Assets	Other non-current assets consist of the following: (In US$ millions) December 31, 2017 December 31, 2016 Deferred tax effect of internal transfer of assets 75 84 Deferred mobilization costs 5 14 Other 1 3 Total other non-current assets 81 101

Long-term debt (Tables)

Long-term debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt	As at December 31, 2017 and 2016 , we had the following debt: (In US$ millions), unless stated otherwise December 31, 2017 December 31, 2016 Secured credit facilities $1,500 million facility (1) 1,112 1,219 $1,350 million facility (1) 931 1,046 $2,000 million facility (NADL) (1) 897 1,033 $1,750 million facility (Sevan Drilling) (1) 856 945 $950 million facility (1) 558 622 $1,450 million facility (1) 318 353 $450 million Eminence facility (1) 261 278 $360 facility (Asia Offshore Drilling) 210 237 $300 million facility (1) 142 162 $400 million facility (1) 133 190 $450 million facility (2015) (1) 101 175 $440 million facility (1) 62 190 Total secured credit facilities 5,581 6,450 Ship Finance Loans $390 million facility (SFL Deepwater) 226 248 $375 million facility (SFL Hercules) 251 279 $475 million facility (SFL Linus) 309 356 Total Ship Finance Loans 786 883 Unsecured bonds $1,000 million bond (2) 843 843 NOK1,800 million bond (2) 231 210 $500 million bond (2) 479 479 NOK1,500 million bond (NADL) (2) 182 165 $ 600 million bond (NADL) (2) 413 413 SEK 1,500 million bond (2) 186 165 Total unsecured bonds 2,334 2,275 Total debt principal 8,701 9,608 Less: Debt balance held as subject to compromise (7,705 ) — Debt balance not subject to compromise 996 9,608 Less: current interest bearing debt not subject to compromise (511 ) (3,230 ) Long-term interest bearing debt not subject to compromise 485 6,378 (1) Denotes impaired secured credit facilities that were reclassified to "Liabilities subject to compromise" on September 12, 2017 (2) Denotes unsecured bonds that were reclassified to "Liabilities subject to compromise" on September 12, 2017
Schedule of Debt Issuance Costs Against Current and Long-Term Debt	Details of the debt issuance costs netted against the non-impaired current and long-term debt for each of the periods presented are shown below. Outstanding balance as at December 31, 2017 (In US$ millions) Principal outstanding Less: Debt issuance costs Total debt Debt due within one year 511 (2 ) 509 Long-term debt 485 — 485 Debt held as subject to compromise 7,705 — 7,705 Total 8,701 (2 ) 8,699 Outstanding debt as at December 31, 2016 (In US$ millions) Principal outstanding Less: Debt issuance costs Total debt Debt due within one year 3,230 (35 ) 3,195 Long-term debt 6,378 (59 ) 6,319 Total 9,608 (94 ) 9,514
Outstanding Debt	The outstanding debt as at December 31, 2017 is repayable as follows: (In US$ millions) December 31, 2017 2018 511 2019 485 Total debt principal (1) 996 (1) Excludes impaired secured debt and unsecured bonds held within "Liabilities subject to compromise"

Other current liabilities (Tabl

Other current liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Other current liabilities	Other current liabilities are comprised of the following: (In US$ millions) December 31, 2017 December 31, 2016 Taxes payable 70 148 Deferred mobilization revenue 37 107 Intangible liabilities - unfavorable contracts (1) 23 43 Employee withheld taxes, social security and vacation payments 15 55 Accrued interest expense 3 69 Construction obligation (2) — 500 Derivative financial instruments (3) — 236 Accrued expenses 103 116 Other current liabilities 17 78 Total other current liabilities (4) 268 1,352 (1) Intangible liabilities represent the estimated fair values of acquired unfavorable drilling contracts. Refer to Note 20 "Goodwill and other intangible assets and liabilities" for more information. (2) A construction obligation was recognized upon the acquisition of Sevan Drilling for the Sevan Developer . On April 27, 2017 the construction obligation increased to $526 million following refunds received from Cosco, taking the delivery installment back to the contract price. In July 2017, Sevan and Cosco agreed to further defer the Sevan Developer delivery until June 30, 2020. The contract amendment included a contract termination clause for Cosco and, as Sevan does not have termination rights, it was deemed to have lost control of the asset and therefore derecognized both the newbuild asset, construction obligation and accrued interest. Refer to Note 6 "(Loss)/gain on disposals" for more information. (3) On filing for Chapter 11, an event of default under each of our derivative agreements was triggered, resulting in the termination of the derivative financial instruments on September 13, 2017. As a result, the outstanding derivative balance was held at the counterparty claimed value within "Liabilities subject to compromise" on the Consolidated Balance Sheet as at December 31, 2017 . Refer to Note 31 "Risk management and financial instruments" for more information. (4) Balances held as at December 31, 2017 exclude liabilities that are subject to compromise, which have been reclassified to a separate line within the Consolidated Balance Sheet. This represents our estimate of known or potential pre-petition claims to be resolved in connection with the Chapter 11 proceedings. Refer to Note 1 "General Information".

Other non-current liabilities (

Other non-current liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Other non-current liabilities	Other non-current liabilities are comprised of the following: (In US$ millions) December 31, 2017 December 31, 2016 Accrued pension liabilities 6 3 Deferred mobilization revenues 18 55 Intangible liabilities - unfavorable contracts (1) — 23 Other non-current liabilities 43 38 Total other non-current liabilities (2) 67 119 (1) Intangible liabilities represent the estimated fair values of acquired unfavorable drilling contracts. Refer to Note 20 - "Goodwill and other intangible assets and liabilities" for more information. (2) Balances held as at December 31, 2017 exclude liabilities that are subject to compromise, which have been reclassified to a separate line within the Consolidated Balance Sheet. This represents our estimate of known or potential pre-petition claims to be resolved in connection with the Chapter 11 proceedings. Refer to Note 1 "General Information".

Common shares (Tables)

Common shares (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Share Capital	December 31, 2017 December 31, 2016 December 31, 2015 All shares are common shares of $2.00 par value each Shares US$ millions Shares US$ millions Shares US$ millions Authorized share capital 800,000,000 1,600 800,000,000 1,600 800,000,000 1,600 Issued and fully paid share capital 508,763,020 1,017 508,763,020 1,017 493,078,680 986 Treasury shares held by the Company (4,244,080 ) (9 ) (4,318,740 ) (9 ) (318,740 ) (1 ) Outstanding shares in issue 504,518,940 1,008 504,444,280 1,008 492,759,940 985

Non-controlling interest (Table

Non-controlling interest (Tables)	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Changes in Non-Controlling Interest	Changes in non-controlling interest for the years ended December 31, 2017 , 2016 and 2015 are as follows: (In US$ millions) Ship Finance International Ltd VIEs North Atlantic Drilling Ltd Asia Offshore Drilling Ltd Sevan Drilling ASA Seadrill Nigeria Operations Limited Total December 31, 2014 32 205 134 251 4 626 Changes in 2015 — 8 (14 ) — (4 ) (10 ) Net income attributable to non-controlling interest in 2015 30 (16 ) 20 59 — 93 Impairment of goodwill (48 ) — (18 ) — — — (28 ) — — (94 ) December 31, 2015 14 179 140 282 — 615 Changes in 2016 (112 ) 7 — — 6 (99 ) Net income attributable to non-controlling interest in 2016 29 (21 ) 9 9 — 26 December 31, 2016 (69 ) 165 149 291 6 542 Changes in 2017 (14 ) — — — — (14 ) Net income attributable to non-controlling interest in 2017 24 (89 ) — (65 ) 1 (129 ) December 31, 2017 (59 ) 76 149 226 7 399

AccumuAccumulated other compreh

AccumuAccumulated other comprehensive income/(loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income	Accumulated other comprehensive income consists of the following: (In US$ millions) Unrealized gain on marketable securities Unrealized gain on foreign exchange Actuarial gain/(loss) relating to pension Share in unrealized gains from associated companies Other Total Balance as at December 31, 2016 17 36 (23 ) 23 — 53 Other comprehensive income before reclassifications 14 — (3 ) 2 2 15 Amounts reclassified from accumulated other comprehensive income — — — (10 ) — (10 ) Balance as at December 31, 2017 31 36 (26 ) 15 2 58

Share based compensation (Table

Share based compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share Option Transactions Related to the Seadrill Scheme	The following table summarizes share option transactions related to the Seadrill Scheme in 2017 , 2016 and 2015 : December 31, 2017 December 31, 2016 December 31, 2015 Options Weighted average exercise price $ Options Weighted average exercise price $ Options Weighted average exercise price $ Outstanding at beginning of year 947,500 20.08 2,015,171 28.53 2,241,116 35.10 Granted — — — — 710,000 12.04 Exercised — — — — — — Forfeited (410,000 ) 22.06 (1,067,671 ) 35.29 (935,945 ) 32.81 Outstanding at end of year 537,500 11.62 947,500 20.08 2,015,171 28.53 Exercisable at end of year 358,959 11.65 412,917 25.79 882,152 36.14
Restricted Stock Unit Activity	The following table summarizes the RSU activity for NADL for the years ended December 31, 2017 , 2016 and 2015 : Restricted Stock Units - NADL December 31, 2017 December 31, 2016 December 31, 2015 Outstanding at beginning of year 413,702 174,583 253,870 Granted — 270,653 1,587,719 Settled — (20,837 ) — Adjustment (1) — — (1,571,251 ) Forfeited (300 ) (10,697 ) (95,755 ) Outstanding at end of year 413,402 413,702 174,583 (1) Adjustment relates to NADL's reverse stock split in December 2015 , as discussed above. The following table summarizes the RSU activity for us for the years ended December 31, 2017 , 2016 and 2015 : Restricted Stock Units - Seadrill December 31, 2017 December 31, 2016 December 31, 2015 Outstanding at beginning of year 5,186,724 1,402,980 525,210 Granted — 4,349,158 937,970 Exercised (74,660 ) (249,050 ) — Forfeited (798,127 ) (316,364 ) (60,200 ) Outstanding at end of year 4,313,937 5,186,724 1,402,980

Pension benefits (Tables)

Pension benefits (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Consolidated Balance Sheet Position	Consolidated Balance Sheet position (In US$ millions) December 31, 2017 December 31, 2016 Accrued pension liabilities - Non-current liabilities 6 3 Less: Deferred tax (Asset) (2 ) (1 ) Shareholders equity 4 2
Annual Pension Cost	Annual pension cost Year ended December 31, (In US$ millions) 2017 2016 2015 Service cost 2 7 12 Interest cost on prior years’ benefit obligation 2 3 4 Gross pension cost for the year 4 10 16 Expected return on plan assets (1 ) (4 ) (3 ) Administration charges — — 1 Net pension cost for the year 3 6 14 Social security cost — 1 2 Amortization of actuarial gains/losses — 1 3 Impact of settlement/curtailment funded status (1 ) (1 ) — Total net pension cost 2 7 19
Funded Status of the Defined Benefit Plan	The funded status of the defined benefit plan (In US$ millions) December 31, 2017 December 31, 2016 Projected benefit obligations at end of period 38 60 Plan assets at market value (33 ) (58 ) Accrued pension liability exclusive social security 5 2 Social security related to pension obligations 1 1 Accrued pension liabilities 6 3
Change in Projected Benefit Obligations	Change in projected benefit obligations (In US$ millions) December 31, 2017 December 31, 2016 Projected benefit obligations at beginning of period 60 130 Interest cost 2 3 Service cost 2 7 Benefits paid (2 ) (3 ) Change in unrecognized actuarial gain (3 ) (28 ) Settlement (24 ) (54 ) Foreign currency translations 3 5 Projected benefit obligations at end of period 38 60
Change in Pension Plan Assets	Change in pension plan assets (In US$ millions) December 31, 2017 December 31, 2016 Fair value of plan assets at beginning of year 58 97 Estimated return 1 4 Contribution by employer 1 9 Administration charges — — Benefits paid (2 ) (3 ) Change in unrecognized actuarial loss (5 ) (1 ) Settlement (23 ) (52 ) Foreign currency translations 3 4 Fair value of plan assets at end of year 33 58
Assumptions Used in Calculation of Pension Obligations	Assumptions used in calculation of pension obligations Year ended December 31, 2017 2016 2015 Rate of compensation increase at the end of year 2.50 % 2.50 % 2.50 % Discount rate at the end of year 2.40 % 2.10 % 2.70 % Prescribed pension index factor 1.50 % 1.20 % 1.20 % Expected return on plan assets for the year 2.40 % 3.00 % 3.30 % Employee turnover 4.00 % 4.00 % 4.00 % Expected increases in Social Security Base 2.25 % 2.25 % 2.50 %
Weighted-Average Asset Allocation of Funds Related to Defined Benefit Plan	The weighted-average asset allocation of funds related to our defined benefit plan at December 31, was as follows: Pension benefit plan assets December 31, 2017 December 31, 2016 Equity securities 10.6 % 7.1 % Debt securities 66.1 % 54.7 % Real estate 8.8 % 9.4 % Money market 13.5 % 28.1 % Other 1.0 % 0.7 % Total 100.0 % 100.0 %
Expected Annual Pension Plan Contributions Under Defined Benefit Plans	The table below shows our expected annual pension plans contributions under defined benefit plans for the years ending December 31, 2018-2027 . The expected payments are based on the assumptions used to measure our obligations at December 31, 2017 and include estimated future employee services. (In US$ millions) December 31, 2017 2018 3 2019 3 2020 3 2021 3 2022 3 2023-2027 15 Total payments expected during the next 10 years 30

Related party transactions (Tab

Related party transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Receivables/(payables) with SeaMex Joint Venture as at December 31, 2017 consisted of the following: (In $ millions) December 31, 2017 December 31, Seller’s credit 250 250 $45 million loan facility 45 45 Interest on long-term funding and sellers credit 50 22 Other receivables 32 31 Other payables (3 ) (2 ) During the years ended December 31, 2017 , 2016 and 2015 , we incurred the following lease costs on units leased from the Ship Finance subsidiaries. Year ended December 31, (US$ millions) 2017 2016 2015 West Hercules 56 57 55 West Taurus 51 52 57 West Linus 83 82 81 Total 190 191 193 These lease costs are eliminated on consolidation. The net income/(expense) with Seadrill Partners for the years ended December 31, 2017 , 2016 , and 2015 were as follows: Year ended December 31, (In US$ millions) 2017 2016 2015 Management fees charged to Seadrill Partners - Other revenues (a) and (b) 75 65 75 Rig operating expenses charged to Seadrill Partners - Other revenues (c) 23 25 29 Contingent consideration 27 21 47 Insurance premiums charged to Seadrill Partners (d) 11 16 20 Rig operating costs charged by Seadrill Partners (e) (5 ) (11 ) (13 ) Bareboat charter arrangements (f) 3 10 (2 ) Intercompany inventory purchases (2 ) (1 ) — Interest expenses charged to Seadrill Partners (g) 6 12 16 Interest recognized on deferred consideration receivable 5 5 8 Derivatives recharged to Seadrill Partners (h) 1 4 10 Net related party income from Seadrill Partners 144 146 190 Receivables/(payables) with Seadrill Partners and its subsidiaries as at December 31, 2017 and 2016 consisted of the following balances: (In US$ millions) December 31, December 31, Rig financing agreements and Loan Agreements (i) 25 160 $109.5 million Vendor financing loan (j) — — Deferred consideration receivable (k) 52 61 Other receivables (l) 157 189 Other payables (l) (24 ) (80 )

Risk management and financial73

Risk management and financial instruments (Restated) (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Realized and Unrealized Gains and Losses	Realized and unrealized gains and losses The total realized and unrealized gains and losses recognized in the Consolidated Statement of Operations relating to our derivative arrangements for the year ended December 31, 2017 , 2016 and 2015 are as follows: Year ended December 31, (In US$ millions) 2017 2016 2015 Gains / (losses) recognized in the Consolidated Statement of Operations relating to derivative financial instruments Interest rate swap agreements not qualified as hedge accounting (31 ) (48 ) (104 ) Cross currency interest rate swaps not qualified as hedge accounting 46 (20 ) (7 ) Foreign currency forwards not qualified as hedge accounting 1 — (9 ) TRS agreements — (6 ) (27 ) Other (5 ) — (3 ) Gain / (loss) on derivative financial instruments 11 (74 ) (150 )
Schedule of Derivatives, by Variable Interest Entities	Below is a summary of the notional amount, fixed interest rate payable and duration of the outstanding principal as at December 31, 2017 . Variable interest entity Outstanding principal as at December 31, 2017 Receive rate Pay rate Length of contract (In US$ millions) SFL Linus Limited (West Linus) 4.0 1 month LIBOR 2.01% Mar 2014 - Oct 2018 SFL Linus Limited (West Linus) 4.0 2 month LIBOR 2.01% Mar 2014 - Nov 2018 SFL Linus Limited (West Linus) 144.5 3 month LIBOR 1.77% Dec 2013 - Dec 2018
Carrying Value and Estimated at Fair Value of Financial Instruments	The carrying value and estimated fair value of our financial instruments that are not measured at fair value on a recurring basis at December 31, 2017 and December 31, 2016 are as follows: Financial assets December 31, 2017 December 31, 2016 (In US$ millions) Fair value Carrying value Fair value Carrying value Cash and cash equivalents 1,255 1,255 1,368 1,368 Restricted cash 104 104 75 75 Related party loans receivable - short term 25 25 174 174 Related party loans receivable - long term 522 515 487 487
Financial Instruments Measured at Fair Value on a Recurring Basis	Financial instruments that are measured at fair value on a recurring basis: Fair value Fair value measurements at reporting date using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs (In US$ millions) December 31, 2017 (Level 1) (Level 2) (Level 3) Assets: Marketable securities - current asset 124 124 — — Convertible debt instrument - non-current asset 52 — — 52 Total assets 176 124 — 52 Fair value Fair value measurements at reporting date using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs (In US$ millions) December 31, 2016 (Level 1) (Level 2) (Level 3) Assets: Marketable securities - current assets 110 110 — — Interest rate swap contracts – non-current assets 4 — 4 — Total assets 114 110 4 — Liabilities: Interest rate swap contracts – current liabilities 41 — 41 — Interest rate swap contracts – non-current liabilities 1 — 1 — Cross currency interest rate swap contracts – current liabilities 194 — 194 — Total liabilities 236 — 236 —

Commitments and contingencies (

Commitments and contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Maturity Schedule for Contractual Commitments	The table below shows the maturity schedule for the newbuilding contractual commitments, which reflects the most recent deferral agreements with Dalian. Refer to Note 3 "Chapter 11 Proceedings" for further information. (In US$ millions) 2018 2019 2020 2021 2022 2023 and thereafter Total Newbuilding commitments 1,685 — — — — — 1,685
Maximum Potential Future Payment for each Type of Guarantee	We have issued guarantees in favor of third parties as follows, which is the maximum potential future payment for each type of guarantee: (In US$ millions) December 31, 2017 December 31, 2016 Guarantees in favor of customers 1, 2 ,3 1,213 1,403 Guarantees in favor of banks 1, 2, 3, 4 698 1,677 Guarantees in favor of suppliers 1, 3, 4 2,200 2,600 Total 4,111 5,680 (1) Guarantees to Seadrill Partners - Within guarantees in favor of customers are guarantees provided on behalf of Seadrill Partners of $165 million ( 2016 : $185 million ). After the insulation of Seadrill Partners from Seadrill in August 2017 there were no guarantees in favor of banks provided on behalf of Seadrill Partners ( 2016 : $621 million ). Guarantees in favor of suppliers includes guarantees on behalf of Seadrill Partners of $0.6 million ( 2016 : $0.4 million ). Refer to Note 30 "Related party transactions" for more information. (2) Guarantees to SeaMex - Within guarantees in favor of customers are guarantees provided on behalf of SeaMex of $30 million ( 2016 : $30 million ). Guarantees in favor of banks includes guarantees on behalf of SeaMex of nil ( 2016 : $0 million ). Refer to Note 30 "Related party transactions" for more information. (3) Guarantees to Archer - Within guarantees provided to customers are guarantees provided on behalf of Archer of $8 million ( 2016 : $8 million ). There were no guarantees in favor of banks provided on behalf of Archer as at December 31, 2017 as these were settled during the year ( 2016 : $253 million and EUR 24 million ( $25 million )). Guarantees in favor of suppliers include guarantees on behalf of Archer of GBP 7 million ( $10 million ) ( 2016 : GBP 8 million ( $10 million )). As of December 31, 2016 , we recognized a $28 million contingent liability to reflect the potential cash settlement of the guarantees. Refer to Note 30 "Related party transactions" for more information. (4) Guarantees to Seabras Sapura - Within guarantees in favor of banks are guarantees provided on behalf of Seabras Sapura Participacoes and Seabras Sapura Holdco totaling $698 million ( 2016 : $787 million ). There were no guarantees in favor of suppliers in relation to our joint venture Seabras Sapura Holdco ( 2016 : nil ). Refer to Note 30 "Related party transactions" for more information.

Operating leases (Tables)

Operating leases (Tables)	12 Months Ended
	Dec. 31, 2017
Leases, Operating [Abstract]
Future Minimum Rental Payments	Future minimum rental payments are as follows: Year (In US$ millions) 2018 12 2019 8 2020 7 2021 7 2022 5 2023 and thereafter 1 Total 40

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2017
Variable Interest Entity, Measure of Activity [Abstract]
Summary of Sale and Leaseback Arrangements	The following table gives a summary of the sale and leaseback arrangements and repurchase options from VIEs, as at December 31, 2017 : Unit Effective from Sale value (In US$ millions) First repurchase option (In US$ millions) Month of first repurchase option Last repurchase option (1) (In US$ millions) Month of last repurchase Option (1) West Taurus Nov 2008 850 418 Feb 2015 149 Nov 2023 West Hercules Oct 2008 850 580 Aug 2011 135 Aug 2023 West Linus June 2013 600 370 Jun 2018 170 Jun 2028 (1) Ship Finance has a right to require us to purchase the West Linus rig on the 15th anniversary for the price of $100 million if we don’t exercise the final repurchase option.
Summary of the Bareboat Charter Rates per Day Based on Base LIBOR Interest Rate for the Next Five Years	A summary of the average bareboat charter rates per day for each unit is given below for the respective years. (In US$ thousands) 2017 2018 2019 2020 2021 2022 West Taurus 158 158 144 143 136 135 West Hercules 170 166 143 141 135 135 West Linus 222 222 173 140 140 133
Assets and Liabilities in the Statutory Accounts of the VIEs	The assets and liabilities in the statutory accounts of the VIEs as at December 31, 2017 and as at December 31, 2016 are as follows: (In US$ millions) December 31, 2017 December 31, 2016 SFL SFL SFL SFL SFL SFL Name of unit West Taurus West Hercules West Linus West Taurus West Hercules West Linus Investment in finance lease 335 326 431 365 360 483 Amount due from related parties 4 4 — 4 4 — Other assets (1) 6 6 8 2 2 — Total assets 345 336 439 371 366 483 Short-term interest bearing debt 226 27 48 23 28 51 Long-term interest bearing debt — 224 261 226 251 305 Other liabilities 3 2 — 3 1 1 Short-term debt due to related parties — — 4 — — — Long-term debt due to related parties (2) 113 80 121 119 86 126 Total liabilities 342 333 434 371 366 483 Equity 3 3 5 — — — Book value of units in the Company's consolidated accounts 385 508 515 409 537 537 (1) Includes cash balance of $17 million as at December 31, 2017 ( December 31, 2016 : nil ). These have been consolidated into the Consolidated Balance Sheet within "Cash and cash equivalents". (2) We present balances due to/from Ship Finance on a net basis, due to the fact that there is a right to offset established in the long-term loan agreements, and the balances are intended to be settled on a net basis. As at December 31, 2016 , the balances offset were $26 million related to SFL Deepwater Ltd and $59 million related to SFL Hercules Ltd against "Long term debt due to related parties" within "Non-current liabilities" in the Consolidated Balance Sheet. As at December 31, 2017 , we have no receivable balances presented against "Long term debt due to related parties" within "Non-current liabilities" in the Consolidated Balance Sheet.

Assets held for sale (Tables)

Assets held for sale (Tables)	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Asset Held-for-sale	(In US$ millions) As at December 31, 2017 As at December 31, 2016 Opening balance at the beginning of the period 128 128 West Rigel newbuild investment, classified as held for sale — — Loss on disposal (2 ) — Non-current assets held for sale 126 128

Supplementary cash flow infor78

Supplementary cash flow information (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Non-cash Investing and Financing Activities	The table below summarizes the non-cash investing and financing activities relating to the periods presented: December 31, 2017 December 31, 2016 December 31, 2015 Non-cash investing activities Disposal of subsidiaries - existing bank loan repaid (1) — — 150 Sale of rigs and equipment (2) 103 — — Increase of investment in Seadrill Mobile Units (Nigeria) Ltd (7) — (6 ) — Proceeds from repayment of short-term loan from related parties due to Seadrill Partners insulation from Seadrill Limited (9) 109 — — Derecognition of Sevan Developer newbuild asset (10) 620 — — Derecognition of Sevan Developer construction obligation (10) (526 ) — — Non-cash financing activities Repayment of bank loan through disposal of subsidiaries (1) — — (150 ) Repayment of debt following sale of rigs and equipment (2) (103 ) — — Repayment relating to share forward contracts and other derivatives (3) — — (136 ) Repayment relating to SapuraKencana financing agreements (4) — (160 ) (93 ) Conversion of convertible bond into shares, decrease in long term debt (5) — (105 ) — Conversion of convertible bond into shares, net increase in equity (5) — 58 — Increase in non-controlling interest in Seadrill Nigeria Operations Ltd (6) — 7 — Proceeds from long-term loans (7) — 150 — Long term loans netted-down with related party balances (7) — (150 ) — Dividend to non-controlling interests in VIEs (8) (14 ) (113 ) — Repayment of debt following insulation of Seadrill Partners from Seadrill Limited (9) (109 ) — — 1. During the year ended December 31, 2015 , existing debt of ours was directly settled as consideration for the disposal of certain drilling rigs to the SeaMex joint venture - refer to Note 6 "(Loss)/gain on disposals" for further information. 2. During the year ended December 31, 2017 , we completed our sale of the West Triton, West Resolute and West Mischief to Shelf Drilling , receiving cash consideration of $122 million . This comprised sales value of $225 million offset by $103 million of debt repayments. Refer to Note 6 "(Loss)/gain on disposals" for further information. 3. During the year ended December 31, 2015 , we settled Sevan share repurchase agreements using cash balances already classified as restricted. 4. During the years ended December 31, 2016 and December 31, 2015 , we settled SapuraKencana financing agreements using cash balances already classified as restricted. 5. In May 2016 , we entered into a privately negotiated exchange agreement with certain holders of our outstanding 5.625% (subsequently increased to 6.125% ) Senior Notes due in 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 8,184,340 new shares of our common stock, par value $2.00 per share, in exchange for $55 million principal amount of the 2017 Notes. Settlement occurred on May 20, 2016 , upon which we had a total of 500,944,280 shares of our common stock issued and outstanding. In June 2016 , we entered into another privately negotiated exchange agreement with certain holders of our outstanding 5.625% (subsequently increased to 6.125% ) Senior Notes due 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 7,500,000 new shares of our common stock, par value $2.00 per share, in exchange for $50 million principal amount of the 2017 Notes. We had a total of 508,444,280 shares of our common stock issued and outstanding, post settlement on June 13, 2016 . 6. On December 5, 2016 , our wholly owned subsidiary Seadrill UK Ltd. acquired a 10% interest that an unrelated party, HH Global Alliance Investments Limited (“HHL”) held in Seadrill Mobile Units (Nigeria) Ltd, the service company for West Capella, for a notional value of $7 million . Simultaneously HHL acquired from Seadrill UK Ltd. a 49% interest in Seadrill Nigeria Operations Limited, the service company for West Jupiter for a notional value of $7 million . The impact of these transactions was to increase Seadrill’s direct ownership interest in Seadrill Partners by $7 million , and to recognize HHL’s non-controlling interest in Seadrill Nigeria Operations Ltd of $7 million . 7. During the year ended December 31, 2016 , certain consolidated VIEs of ours withdrew bank loans and made loans to the related party Ship Finance International. These balances are presented net in the consolidated statement of cash flows. Refer to Note 22 "Long-term debt" for further information. 8. During the year ended December 31, 2017 , the Ship Finance VIEs that we consolidate declared dividends payable totaling $14 million to Ship Finance ( December 31, 2016 : $113 million ). Refer to Note 34 "Variable interest entities" for further information. 9. In August 2017, Seadrill Partners amended certain credit facilities to insulate itself from Seadrill Limited. This resulted in a $109 million repayment in respect to the $440 million secured debt facility. Refer to Note 30 "Related party transactions" for further information on related party transactions.

General information (Details)

General information (Details) $ in Millions	Sep. 12, 2017USD ($)drilling_unit	Dec. 31, 2017drilling_unit
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of offshore drilling units owned by the Company		35
Number of offshore drilling units under construction		13
Number of chartered drilling units	3
Amount of new cash commitments in the form of new notes and equity | $	$ 1,060
Percentage of voting control for certain variable interest entities (in hundredths)		50.00%

Accounting policies (Details)

Accounting policies (Details) - USD ($)	Jan. 01, 2018	Nov. 30, 2010	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Capitalized interest cost			$ 0
Threshold percentage for recognizing actuarial gains and losses (in hundredths)			10.00%
Vesting period		12 months
Retained earnings			$ 225,000,000		$ 3,198,000,000
Other current assets			(257,000,000)		(495,000,000)
Total restricted cash			$ 104,000,000		$ 75,000,000
Overhauls of drilling units
Property, Plant and Equipment [Line Items]
Estimated economic useful life			5 years
Drilling units
Property, Plant and Equipment [Line Items]
Estimated economic useful life			30 years
Period within which management is actively committed to a probable sale of assets classified as held for sale			1 year
Equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated economic useful life			3 years
Equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated economic useful life			5 years
Restricted Stock Units (RSUs)
Property, Plant and Equipment [Line Items]
Vesting period			3 years
Subsequent Event | Accounting Standards Update 2016-01
Property, Plant and Equipment [Line Items]
Fair value gains from AOCI	$ 32,000,000
Retained earnings	32,000,000
Subsequent Event | Accounting Standards Update 2016-16
Property, Plant and Equipment [Line Items]
Retained earnings	(84,000,000)
Other current assets	$ 84,000,000
Scenario, Forecast | Accounting Standards Update 2016-02 | Minimum
Property, Plant and Equipment [Line Items]
Operating Lease, Right-of-Use Asset				$ 30,000,000
Scenario, Forecast | Accounting Standards Update 2016-02 | Maximum
Property, Plant and Equipment [Line Items]
Operating Lease, Right-of-Use Asset				$ 50,000,000

Chapter 11 Proceedings (Details

Chapter 11 Proceedings (Details)

Feb. 28, 2018USD ($)

Feb. 26, 2018USD ($)

Sep. 12, 2017USD ($)drilling_unit

Aug. 31, 2017credit_facility

Jun. 30, 2017USD ($)

Apr. 30, 2017USD ($)

Mar. 31, 2018USD ($)claim

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

[1]

Jul. 31, 2017USD ($)

Dec. 31, 2013USD ($)

Dec. 31, 2012USD ($)

Dec. 31, 2011USD ($)

Fresh-Start Adjustment [Line Items]

Number of amended credit facilities | credit_facility

3

Number of chartered drilling units | drilling_unit

3

Amount of new cash commitments in the form of new notes and equity

$ 1,060,000,000

Number of days after Confirmation Date the plan must effective by

90 days

Plan of reorganization, equity securities issued or to be issued, ownership percentage

2.00%

Protection payments

$ 81,000,000

Liabilities subject to compromise, accrued interest

129,000,000

Debtor reorganization items, claims settlement accrual

1,064,000,000

Loss on impairment of long lived assets

696,000,000

$ 44,000,000

$ 563,000,000

Payments for debtor reorganization items

72,000,000

New investor commitment fees

(53,000,000)

Subsequent Event

Fresh-Start Adjustment [Line Items]

Amount of new cash commitments in the form of new notes and equity

$ 1,080,000,000

Extension period

3 months

Plan of reorganization, subject to termination, duration after petition date for bankruptcy filed

11 months

Plan of reorganization, percentage of equity securities issued or to be issued

15.00%

Bankruptcy claims, unsecured claims, pro rata cash recovery pool

$ 23,000,000

Plan of reorganization, equity securities issued or to be issued, ownership percentage

2.00%

Notes rights offering, pro rata equity securities issued or to be issued, ownership percentage

57.50%

Notes rights offering, maximum value of common shares issued

$ 48,100,000

Plan of reorganization, equity securities issued or to be issued, proceeds from issuance

200,000,000

Plan of reorganization, maximum reduction to cash paid, investment agreement

$ 48,100,000

Bankruptcy claims, number claims filed | claim

1,575

Bankruptcy claims, amount of claims filed

$ 19,200,000,000

$400 million facility | Secured Debt

Fresh-Start Adjustment [Line Items]

Debt, face amount

400,000,000

$ 400,000,000

$ 400,000,000

$450 million Eminence facility | Secured Debt

Fresh-Start Adjustment [Line Items]

Debt, face amount

450,000,000

Maximum borrowing capacity

450,000,000

$ 450,000,000

$440 million facility | Secured Debt

Fresh-Start Adjustment [Line Items]

Debt, face amount

440,000,000

$ 440,000,000

$ 440,000,000

New Secured Notes | Secured Debt | Subsequent Event

Fresh-Start Adjustment [Line Items]

Plan of reorganization, debt securities issued or to be issued, value

$ 880,000,000

Archer Limited (Archer)

Fresh-Start Adjustment [Line Items]

Payment for debt extinguishment

$ 3,000,000

$ 25,000,000

Archer Limited (Archer) | Financial Guarantee

Fresh-Start Adjustment [Line Items]

Extinguished financial guarantees

$ 25,000,000

$ 253,000,000

Holders of General Unsecured Claims | Subsequent Event

Fresh-Start Adjustment [Line Items]

Payment for debt extinguishment

17,000,000

Shipyards | Subsequent Event

Fresh-Start Adjustment [Line Items]

Payment for debt extinguishment

$ 17,000,000

Commitment Parties | Subsequent Event

Fresh-Start Adjustment [Line Items]

Plan of reorganization, percentage of equity securities issued or to be issued

25.00%

Hemen | Subsequent Event

Fresh-Start Adjustment [Line Items]

Plan of reorganization, percentage of equity securities issued or to be issued

5.00%

Other Commitment Parties | Subsequent Event

Fresh-Start Adjustment [Line Items]

Plan of reorganization, percentage of equity securities issued or to be issued

0.50%

Stock Options | Employee Incentive Plan | Subsequent Event

Fresh-Start Adjustment [Line Items]

Plan of reorganization, share-based compensation arrangement, percentage of shares available for grant

10.00%

West Dorado, West Draco, West Aquila and West Libra

Fresh-Start Adjustment [Line Items]

Loss on impairment of long lived assets

$ 696,000,000

[1]

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Chapter 11 Proceedings - Schedu

Chapter 11 Proceedings - Schedule of Reorganization Items (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reorganizations [Abstract]
Advisory and professional fees	$ (66)
New investor commitment fees	(53)
Unamortized debt issuance costs	(66)
Gain or loss on pre-petition allowable claims	(3)
Loss on Newbuilding global settlement agreement	(1,064)
Interest income on surplus cash invested	4
Reversal of issuing entities credit risk on derivatives	(89)
Reorganization items, net	$ (1,337)	$ 0	$ 0

Chapter 11 Proceedings - Sche83

Chapter 11 Proceedings - Schedule of Liabilities Subject to Compromise (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fresh-Start Adjustment [Line Items]
Debt held as subject to compromise	$ 7,705	$ 0
Derivatives previously recorded at fair value	249
Loss on Newbuilding global settlement agreement	1,064
Accounts payable and other liabilities	103
Accrued interest payable	50
Amount due to related party	20
Liabilities subject to compromise	9,191	$ 0
Senior undersecured or impaired external debt
Fresh-Start Adjustment [Line Items]
Debt held as subject to compromise	2,334
Unsecured bonds
Fresh-Start Adjustment [Line Items]
Debt held as subject to compromise	$ 5,371

Chapter 11 Proceedings - Conden

Chapter 11 Proceedings - Condensed Combined Debtor-In-Possession Financial Information (Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Cash and cash equivalents	$ 1,255	$ 1,368	$ 1,044	[1]	$ 831	[1]
Total restricted cash	104	75
Marketable securities	124	110
Accounts receivables, net	295	462
Amount due from related parties - current	217	376
Other current assets	257	495
Total current assets	2,252	2,886
Investment in associated companies	1,473	2,168
Newbuildings	248	1,531
Drilling units	13,216	14,276
Deferred tax assets	78	60
Equipment	29	41
Seller’s credit	547	523
Assets held for sale - non-current	126	128
Other non-current assets	81	101
Total non-current assets	15,730	18,780
Total assets	17,982	21,666
Debt due within one year	509	3,195
Trade accounts payable	72	93
Amounts due to related parties - current	10	83
Other current liabilities	268	1,352
Total current liabilities	859	4,723
Liabilities Subject to Compromise	9,191	0
Long-term debt	485	6,319
Long-term debt due to related parties	314	330
Deferred tax liabilities	107	112
Other non-current liabilities	67	119
Total non-current liabilities	973	6,880
Total equity	6,959	10,063	$ 10,068		$ 10,390
Total liabilities and equity	17,982	21,666
Consolidated Entities Under Chapter 11 Bankruptcy
Cash and cash equivalents	1,157	$ 990
Total restricted cash	81
Marketable securities	124
Accounts receivables, net	291
Amount due from related parties - current	213
Intra group receivables	1,064
Other current assets	257
Total current assets	3,187
Investment in associated companies	1,346
Drilling units	12,568
Shares in subsidiaries	6,501
Deferred tax assets	10
Equipment	29
Seller’s credit	547
Intra group non-current assets	475
Other non-current assets	81
Total non-current assets	21,557
Total assets	24,744
Trade accounts payable	69
Amounts due to related parties - current	6
Intra group liabilities	961
Other current liabilities	240
Total current liabilities	1,276
Liabilities Subject to Compromise	9,191
Deferred tax liabilities	108
Intra group non-current liabilities	1,434
Other non-current liabilities	69
Total non-current liabilities	1,611
Total equity	12,666
Total liabilities and equity	$ 24,744
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Chapter 11 Proceedings - Cond85

Chapter 11 Proceedings - Condensed Combined Debtor-In-Possession Financial Information (Income Statement) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Contract revenues		$ 1,888,000,000	$ 2,850,000,000	$ 3,957,000,000
Reimbursable revenues		38,000,000	66,000,000	113,000,000
Intra group revenues		110,000,000	100,000,000	119,000,000
Other revenues	[1]	162,000,000	253,000,000	265,000,000
Total operating revenues		2,088,000,000	3,169,000,000	4,335,000,000
Loss on disposals	[1]	(245,000,000)	0	(63,000,000)
Contingent consideration realized	[1]	27,000,000	21,000,000	47,000,000	[2]
Vessel and rig operating expenses	[1]	(792,000,000)	(1,015,000,000)	(1,611,000,000)
Reimbursable expenses		(35,000,000)	(61,000,000)	(99,000,000)
Depreciation and amortization		(798,000,000)	(810,000,000)	(779,000,000)	[2]
Impairment of Long-Lived Assets Held-for-use		(696,000,000)	(44,000,000)	(563,000,000)	[2]
Total operating expenses		(2,598,000,000)	(2,164,000,000)	(3,300,000,000)
Operating income		(728,000,000)	1,026,000,000	1,019,000,000
Interest expense	[1]	(285,000,000)	(412,000,000)	(415,000,000)
Share in results from associated companies (net of tax)		174,000,000	283,000,000	192,000,000
Loss on impairment of investments		(841,000,000)	(895,000,000)	(1,285,000,000)
(Loss)/gain on derivative financial instruments	[1]	11,000,000	(74,000,000)	(150,000,000)
Foreign exchange (loss)/gain		(65,000,000)	18,000,000	63,000,000
Reorganization items, net		(1,337,000,000)	0	0
Other financial items and other income, net	[1]	(44,000,000)	(15,000,000)	52,000,000
Total financial items and other (expense)/income, net		(2,308,000,000)	(982,000,000)	(1,446,000,000)
Loss before income taxes		(3,036,000,000)	44,000,000	(427,000,000)
Income tax expense		66,000,000	199,000,000	208,000,000
Net (loss)/income		(3,102,000,000)	(155,000,000)	(635,000,000)	[2],[3]
Net (loss)/income attributable to the non-controlling interest		(129,000,000)	26,000,000	(1,000,000)
Net loss attributable to the parent		(2,973,000,000)	$ (181,000,000)	$ (634,000,000)
Consolidated Entities Under Chapter 11 Bankruptcy
Contract revenues		463,000,000
Reimbursable revenues		12,000,000
Intra group revenues		27,000,000
Other revenues		1,000,000
Total operating revenues		503,000,000
Loss on disposals		(95,000,000)
Contingent consideration realized		9,000,000
Vessel and rig operating expenses		(262,000,000)
Reimbursable expenses		(11,000,000)
Depreciation and amortization		(229,000,000)
Intra group expenses		(16,000,000)
Impairment of Long-Lived Assets Held-for-use		(696,000,000)
Total operating expenses		(1,214,000,000)
Operating income		(797,000,000)
Interest expense		21,000,000
Share in results from associated companies (net of tax)		67,000,000
Loss on impairment of investments		(841,000,000)
(Loss)/gain on derivative financial instruments		(2,000,000)
Foreign exchange (loss)/gain		8,000,000
Reorganization items, net		(1,337,000,000)
Other financial items and other income, net		8,000,000
Total financial items and other (expense)/income, net		(2,076,000,000)
Loss before income taxes		(2,873,000,000)
Income tax expense		(67,000,000)
Net (loss)/income		(2,940,000,000)
Net (loss)/income attributable to the non-controlling interest		(67,000,000)
Net loss attributable to the parent		$ (2,873,000,000)
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".
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Chapter 11 Proceedings - Cond86

Chapter 11 Proceedings - Condensed Combined Debtor-In-Possession Financial Information (Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015	[1]
Net cash provided by operating activities	$ 399	$ 1,184		$ 1,788
Additions to newbuildings	(33)	(52)		(613)
Additions to drilling units and equipment	(59)	(84)		(322)
Contingent consideration received	95	95		27
Change in restricted cash	(29)	(26)		(25)
Net cash provided by investing activities	329	328		(190)
Repayments of debt	(754)	(1,054)		(2,999)
Debt fees paid	(53)	(31)		(16)
Net cash used in financing activities	(846)	(1,206)		(1,370)
Effect of exchange rate changes on cash and cash equivalents	5	18		(15)
Net increase in cash and cash equivalents	(113)	324		213
Cash and cash equivalents at beginning of the year	1,368	1,044	[1]	831
Cash and cash equivalents at the end of year	1,255	1,368		$ 1,044
Consolidated Entities Under Chapter 11 Bankruptcy
Net cash provided by operating activities	294
Additions to newbuildings	(1)
Additions to drilling units and equipment	(20)
Contingent consideration received	28
Change in restricted cash	(10)
Proceed from repayment of short term loan to related parties	8
Net cash provided by investing activities	5
Repayments of debt	(77)
Debt fees paid	(53)
Net cash used in financing activities	(130)
Effect of exchange rate changes on cash and cash equivalents	(2)
Net increase in cash and cash equivalents	167
Cash and cash equivalents at beginning of the year	990
Cash and cash equivalents at the end of year	$ 1,157	$ 990
[1]	Text selection found with no content.

Segment information (Details)

Segment information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	3
Revenues	$ 2,088	$ 3,169	$ 4,335
Depreciation and amortization	798	810	779	[1]
Operating Income - net income [Abstract]
Operating income	(728)	1,026	1,019
Unallocated items:
Total financial items and other	(2,308)	(982)	(1,446)
(Loss)/income before income taxes	(3,036)	44	(427)
Book value on disposal	13,464	15,807
Assets held for sale	126	128
Investments in Associated companies	1,473	2,168
Marketable securities	124	110
Cash and restricted cash	1,359	1,443
Other assets	1,436	2,010
Total assets	17,982	21,666
Capital expenditures - fixed assets	150	227	1,045
Floaters
Segment Reporting Information [Line Items]
Revenues	1,387	2,212	2,906
Depreciation and amortization	601	600	570
Operating Income - net income [Abstract]
Operating income	(622)	759	340
Unallocated items:
Book value on disposal	9,956	11,751
Capital expenditures - fixed assets	128	192	950
Jack-up rigs
Segment Reporting Information [Line Items]
Revenues	617	865	1,293
Depreciation and amortization	197	210	208
Operating Income - net income [Abstract]
Operating income	(112)	267	664
Unallocated items:
Book value on disposal	3,508	4,056
Capital expenditures - fixed assets	22	35	95
Other
Segment Reporting Information [Line Items]
Revenues	84	92	136
Depreciation and amortization	0	0	1
Operating Income - net income [Abstract]
Operating income	$ 6	$ 0	$ 15
[1]	Text selection found with no content.

Segment Information - Geographi

Segment Information - Geographic (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue		$ 2,088	$ 3,169	$ 4,335
Fixed assets - operating drilling units	[1]	13,216	12,853
Angola
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue		482	419	527
Spain
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue		358	491	877
Fixed assets - operating drilling units	[1]	1,816	1,884
MALAYSIA
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed assets - operating drilling units	[1]	1,809	673
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue		291	370	371
Fixed assets - operating drilling units	[1]	1,266	1,298
Norway
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue		219	475	641
Fixed assets - operating drilling units	[1]	2,258	2,456
SPAIN
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed assets - operating drilling units	[1]	2,016	944
Nigeria
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue		193	431	499
Others
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue	[2]	545	983	$ 1,420
Fixed assets - operating drilling units	[1],[3]	$ 4,051	$ 5,598
[1]	The fixed assets referred to in the table above exclude assets under construction. Asset locations at the end of a period are not necessarily indicative of the geographic distribution of the revenues or operating profits generated by such assets during such period.
[2]	Other countries represent countries in which we operate that individually had revenues representing less than 10% of total revenues earned for any of the periods presented.
[3]	Other countries represent countries in which we operate that individually had fixed assets representing less than 10% of total fixed assets for any of the periods presented.

Segment information - Major Cus

Segment information - Major Customers (Details) - Contract Revenues - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total S.A Group (Total)
Revenue, Major Customer [Line Items]
Concentration risk percentage	25.00%	18.00%	16.00%
Petroleo Brasileiro S.A (Petrobras)
Revenue, Major Customer [Line Items]
Concentration risk percentage	19.00%	17.00%	19.00%
LLOG
Revenue, Major Customer [Line Items]
Concentration risk percentage	15.00%	13.00%	9.00%
Exxon Mobil Corp (Exxon)
Revenue, Major Customer [Line Items]
Concentration risk percentage	7.00%	13.00%	14.00%
Statoil ASA (Statoil)
Revenue, Major Customer [Line Items]
Concentration risk percentage	4.00%	10.00%	12.00%

Other revenues (Details)

Other revenues (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 31, 2017
Variable Interest Entity [Line Items]
Revenues related party		$ 110	$ 100	$ 119
Amortization of unfavorable contracts		43	65	116
External management fees with third parties		1	19	30
Termination revenue		8	69	0
Total	[1]	162	253	$ 265
West Hercules
Variable Interest Entity [Line Items]
Termination revenue		8
Contract Termination Fee		$ 66
Deferred gain on contract termination			58		$ 8
West Epsilon
Variable Interest Entity [Line Items]
Deferred gain on contract termination			$ 11
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

Loss on disposals (Details)

Loss on disposals (Details) - USD ($)		Oct. 12, 2015	Jun. 19, 2015	Mar. 10, 2015	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Book value on disposal						$ 13,464,000,000	$ 15,807,000,000
Loss on disposal	[1]					(245,000,000)	0	$ (63,000,000)
Exploration and Production Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Book value on disposal						13,216,000,000	14,276,000,000
Total, by property, plant, and equipment disposals
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount						351,000,000
Total, by property, plant, and equipment disposals | Exploration and Production Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount							0
Book value on disposal						596,000,000	0
Loss on disposal						(245,000,000)	$ 0
Total, by property, plant, and equipment disposals | Jack-up rigs
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount								1,802,000,000
Book value on disposal								1,865,000,000
Loss on disposal								(63,000,000)
Sale of West Triton | Exploration and Production Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount						75,000,000
Book value on disposal						109,000,000
Loss on disposal						(34,000,000)
Sale of West Mischief | Exploration and Production Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount						75,000,000
Book value on disposal						146,000,000
Loss on disposal						(71,000,000)
Sale of West Resolute | Exploration and Production Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount						75,000,000
Book value on disposal						136,000,000
Loss on disposal						(61,000,000)
Disposal of Sevan Developer contract | Exploration and Production Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount						0
Book value on disposal						75,000,000
Loss on disposal					$ (75,000,000)	(75,000,000)
Sale of West Rigel | Exploration and Production Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount						126,000,000
Book value on disposal						128,000,000
Loss on disposal						(2,000,000)
Sale of West Rigel | Jack-up rigs
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount								128,000,000
Book value on disposal								210,000,000
Loss on disposal								(82,000,000)
Other | Exploration and Production Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount						0
Book value on disposal						2,000,000
Loss on disposal						$ (2,000,000)
Other | Jack-up rigs
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount								0
Book value on disposal								5,000,000
Loss on disposal								(5,000,000)
Cancellation of West Mira | Exploration and Production Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal		$ (80,000,000)
Cancellation of West Mira | Jack-up rigs
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount								199,000,000
Book value on disposal								279,000,000
Loss on disposal								(80,000,000)
Sale of West Polaris
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount			$ 235,000,000
Loss on disposal			$ (77,000,000)
Sale of West Polaris | Jack-up rigs
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount								235,000,000
Book value on disposal								312,000,000
Loss on disposal								(77,000,000)
SeaMex Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount				$ 1,077,000,000
Loss on disposal				$ 181,000,000
SeaMex Limited | Jack-up rigs
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds/recoverable amount								1,240,000,000
Book value on disposal								1,059,000,000
Loss on disposal								$ 181,000,000
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

Loss on disposals - Narrative (

Loss on disposals - Narrative (Details)

Apr. 29, 2017USD ($)

Mar. 13, 2017USD ($)

Oct. 12, 2015USD ($)

Sep. 14, 2015USD ($)

Jul. 31, 2017USD ($)

Oct. 31, 2014option

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Apr. 05, 2018USD ($)

Apr. 27, 2017USD ($)

Dec. 02, 2015USD ($)

Oct. 30, 2015USD ($)

Jun. 19, 2015

Mar. 10, 2015

Mar. 09, 2015

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Loss on disposals

[1]

$ (245,000,000)

$ 0

$ (63,000,000)

Purchase obligation

1,685,000,000

4,098,000,000

Newbuildings

248,000,000

1,531,000,000

Receivable from ship-yard

[2]

0

170,000,000

Loss on impairment of long lived assets

696,000,000

44,000,000

563,000,000

[3]

Book value on disposal

13,464,000,000

15,807,000,000

Assets held for sale - non-current

126,000,000

128,000,000

Total, by property, plant, and equipment disposals

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Fair value of consideration received

351,000,000

Cancellation of West Mira

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Newbuildings

$ 315,000,000

Pre-delivery installments

170,000,000

Redeployed equipment amount

$ 48,000,000

Exploration and Production Equipment

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Book value on disposal

13,216,000,000

14,276,000,000

Exploration and Production Equipment | Total, by property, plant, and equipment disposals

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Fair value of consideration received

0

Loss on disposals

(245,000,000)

0

Book value on disposal

596,000,000

0

Exploration and Production Equipment | West Triton, West Mischief and West Resolute

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Fair value of consideration received

$ 225,000,000

Loss on disposals

$ (166,000,000)

Exploration and Production Equipment | Disposal of Sevan Developer contract

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Fair value of consideration received

0

Loss on disposals

$ (75,000,000)

(75,000,000)

Disposal group, including discontinued operation, property, plant and equipment

620,000,000

Disposal group, including discontinued operation, construction payable

526,000,000

Disposal group, including discontinued operation, accrued liabilities

$ 19,000,000

Book value on disposal

75,000,000

Exploration and Production Equipment | Cancellation of West Mira

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Loss on disposals

$ (80,000,000)

Installment payments reclassified to receivables

170,000,000

Installment payments reclassified to receivables, accrued interest

$ (29,000,000)

Cash proceeds from settlement of cancelled construction contract

$ (170,000,000)

Loss on impairment of long lived assets

44,000,000

Exploration and Production Equipment | Cancellation of West Mira | Loss on Impairment of Long-Lived Assets

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Loss on impairment of long lived assets

31,000,000

Exploration and Production Equipment | Cancellation of West Mira | Interest Income

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Loss on impairment of long lived assets

13,000,000

Exploration and Production Equipment | Sale of West Rigel

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Fair value of consideration received

126,000,000

Loss on disposals

(2,000,000)

Book value on disposal

128,000,000

Assets held for sale - non-current

126,000,000

Exploration and Production Equipment | Sale of West Rigel | Gain (Loss) on Disposal

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Book value on disposal

$ 210,000,000

Exploration and Production Equipment | Sale of West Rigel | Assets held for sale

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Loss on disposals

(2,000,000)

0

Assets held for sale - non-current

126,000,000

128,000,000

$ 128,000,000

Sevan Drilling ASA

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Purchase obligation, minimum deferred delivery period

12 months

Purchase obligations, number of subsequent options in agreement | option

4

Purchase obligation, exercisable interval period

6 months

Purchase obligation

$ 526,000,000

$ 480,000,000

Ownership interest prior to disposal (as percent)

50.11%

Sevan Drilling

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Purchase obligation, refund

$ 26,300,000

Purchase obligation, refund (as percent)

5.00%

Remaining refund amount

$ 26,300,000

Purchase obligation

$ 526,000,000

SeaMex Limited

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Ownership interest prior to disposal (as percent)

100.00%

Other Current Assets | Cancellation of West Mira

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Receivable from ship-yard

$ 170,000,000

SeaMex Limited

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Third party ownership interest (as percent)

50.00%

50.00%

Ownership interest (as percent)

50.00%

50.00%

50.00%

50.00%

100.00%

Seadrill Operating LP

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Ownership interest (as percent)

42.00%

Subsequent Event | Jurong Shipyard | Exploration and Production Equipment | Sale of West Rigel

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Fair value of consideration received

$ 126,000,000

[1]

Includes transactions with related parties. Refer to Note 30 "Related party transactions".

[2]

The receivable from shipyard relates to the West Mira, which reached settlement for $170 million on March 13, 2017. For details on the arbitration process and subsequent settlement, refer to Note 6 "Loss on disposals" for more information.

[3]

Text selection found with no content.

(Loss)_gain on disposals - Cont

(Loss)/gain on disposals - Contingent Consideration (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total contingent consideration recognized	[1]		$ 27	$ 21	$ 47	[2]
West Polaris earn out realized
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total contingent consideration recognized		$ 32	13
West Polaris earn out realized | Sale of business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total contingent consideration recognized			13	8	32
West Vela earn out realized | Sale of business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total contingent consideration recognized			$ 14	$ 13	$ 15
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".
[2]	Text selection found with no content.

Interest expense (Details)

Interest expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Expense [Abstract]
Gross interest expense	$ 313,000,000	$ 451,000,000	$ 475,000,000
Capitalized interest	(28,000,000)	(39,000,000)	(60,000,000)
Interest expense	285,000,000	$ 412,000,000	$ 415,000,000
Protection payments	81,000,000
Capitalized interest cost	$ 0

Impairment loss on marketable95

Impairment loss on marketable securities and investments in associated companies (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended		12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Total impairment of marketable securities investments (reclassification from OCI)				$ 0	$ 153	$ 752
Total impairment of investments				841	895	1,285
Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of investments		$ 73		805	653	533
SapuraKencana
Schedule of Equity Method Investments [Line Items]
Total impairment of marketable securities investments (reclassification from OCI)			$ 167	0	0	178
SeaMex Limited
Schedule of Equity Method Investments [Line Items]
Total impairment of investments		76		36	76	0
Itaunas Drilling, Camburi Drilling, and Sahy Drilling
Schedule of Equity Method Investments [Line Items]
Total impairment of investments				0	13	0
Seadrill Partners, Seamex Limited and Itaunas Drilling, Camburi Drilling, and Sahy Drilling
Schedule of Equity Method Investments [Line Items]
Total impairment of investments				841	742	533
Common Units | Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of marketable securities investments (reclassification from OCI)			574	0	153
Direct Ownership Interest | Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of investments		400	(302)	723	400	302
Subordinated Units | Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of investments	$ 0	$ 180	$ (125)	82	180	125
Member Interest and Incentive Distribution Rights | Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of investments				$ 0	$ 73	$ 106

Impairment loss on marketable96

Impairment loss on marketable securities and investments in associated companies - Seadrill Partners - Subordinated units and direct ownership interests - Impairment of Equity Method Investment (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended		12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Total impairment of investments				$ 841	$ 895	$ 1,285
Remaining economic lives of underlying assets					30 years
Weighted average cost of capital (as percent)					10.00%
Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of investments		$ 73		$ 805	$ 653	533
Subordinated Units and Direct Ownership Interest | Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Remaining economic lives of underlying assets				30 years
Weighted average cost of capital (as percent)				9.75%
Subordinated Units | Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of investments	$ 0	180	$ (125)	$ 82	180	125
Direct Ownership Interest | Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of investments		$ 400	$ (302)	$ 723	$ 400	$ 302

Impairment loss on marketable97

Impairment loss on marketable securities and investments in associated companies - SeaMex Limited (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 10, 2015	Mar. 09, 2015
Schedule of Equity Method Investments [Line Items]
Remaining economic lives of underlying assets			30 years
Weighted average cost of capital (as percent)			10.00%
Total impairment of investments		$ 841	$ 895	$ 1,285
SeaMex Limited
Schedule of Equity Method Investments [Line Items]
Remaining economic lives of underlying assets		30 years
Weighted average cost of capital (as percent)	11.00%	10.25%
Total impairment of investments	$ 76	$ 36	$ 76	$ 0
Third party ownership interest (as percent)				50.00%	50.00%
Ownership interest (as percent)		50.00%	50.00%	50.00%	50.00%	100.00%

Impairment loss on marketable98

Impairment loss on marketable securities and investments in associated companies - Seadrill Partners - Common Units (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Total impairment of marketable securities investments (reclassification from OCI)			$ 0	$ 153		$ 752
Gross unrealized gain			(36)	(52)		$ (476)
Seadrill Partners LLC
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Increase (decrease) in price per unit (as percent)	(20.00%)
Common Unit | Seadrill Partners LLC
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Increase (decrease) in price per unit (as percent)					62.00%
Total impairment of marketable securities investments (reclassification from OCI)		$ 574	$ 0	$ 153
Common units market value (in dollars per share)				$ 4.20	$ 3.53

Impairment loss on marketable99

Impairment loss on marketable securities and investments in associated companies - Seadrill Partners - Member interest - Impairment of Cost method investments (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Total impairment of investments			$ 841	$ 895	$ 1,285
Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of investments	$ 73		$ 805	$ 653	$ 533
Incentive Distribution Rights | Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Total impairment of investments		$ (106)

Impairment loss on marketabl100

Impairment loss on marketable securities and investments in associated companies - Itaunas Drilling, Camburi Drilling, and Sahy Drilling - Impairment of investment in Joint Venture (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)drillship	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Schedule of Equity Method Investments [Line Items]
Total impairment of investments	$ 841	$ 895	$ 1,285
Itaunas Drilling, Camburi Drilling, and Sahy Drilling
Schedule of Equity Method Investments [Line Items]
Number of newbuilding contracts for drillships | drillship	1
Ownership percentage held by equity method investee (as percent)	70.00%
Ownership interest (as percent)	30.00%
Total impairment of investments	$ 0	$ 13	$ 0

Impairment loss on marketabl101

Impairment loss on marketable securities and investments in associated companies - SapuraKencana - Impairment of marketable securities (Details) - USD ($) $ in Millions	Apr. 27, 2016	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015		Sep. 30, 2015
Schedule of Equity Method Investments [Line Items]
Total impairment of marketable securities investments (reclassification from OCI)				$ 0	$ 153	$ 752
Marketable securities				124	110
Loss on impairment of investments				841	895	1,285	[1]
SapuraKencana
Schedule of Equity Method Investments [Line Items]
Increase (decrease) in price per unit (as percent)								(45.00%)
Total impairment of marketable securities investments (reclassification from OCI)			$ 167	0	0	178
Marketable securities						$ 195
Proceeds from available-for-sale securities	$ 195
Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Increase (decrease) in price per unit (as percent)		(20.00%)
Marketable securities				$ 96	$ 110
[1]	Text selection found with no content.

Taxation - Components of Income

Taxation - Components of Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax expense:
Bermuda	$ 0	$ 0	$ 0
Foreign	56	151	177
Deferred tax expense:
Bermuda	0	0	0
Foreign	10	48	31
Total tax expense	$ 66	$ 199	$ 208
Effective tax rate	(2.20%)	452.30%	(48.70%)

Taxation - Narrative (Details)

Taxation - Narrative (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Effective tax rate (as percent)		(2.20%)	452.30%	(48.70%)
Reorganization items, net		$ (1,337,000,000)	$ 0	$ 0
Loss on impairment of investments		841,000,000	895,000,000	1,285,000,000
Loss on derivative financial instruments	[1]	(11,000,000)	74,000,000	150,000,000
Loss on disposals	[1]	(245,000,000)	$ 0	$ (63,000,000)
Statutory income tax rate (in hundredths) (as a percent)			0.00%	0.00%
Unremitted earnings of subsidiaries		37,000,000	$ 34,000,000
Net operating losses carried forward		255,000,000	272,000,000
Deferred tax assets not subject to expiration		248,000,000	237,000,000
Deferred tax assets subject to expiration		7,000,000	35,000,000
Valuation allowance		230,000,000	245,000,000
Unrecognized tax benefits		55,000,000	44,000,000	$ 9,000,000	$ 9,000,000
Accrued interest and penalties		12,000,000	2,000,000
Unrecognized tax benefits, interest and penalties expensed during period		10,000,000	2,000,000	$ 0
Unrecognized tax benefits that would have a favorable impact on effective tax rate		48,000,000
Other Current Liabilities
Related Party Transaction [Line Items]
Unrecognized tax benefits		3,000,000
Other Noncurrent Liabilities
Related Party Transaction [Line Items]
Unrecognized tax benefits		45,000,000
Deferred Tax Asset Reduction
Related Party Transaction [Line Items]
Unrecognized tax benefits		19,000,000
NOL
Related Party Transaction [Line Items]
Valuation allowance		$ 216,000,000	238,000,000
Bermuda
Related Party Transaction [Line Items]
Statutory income tax rate (in hundredths) (as a percent)		0.00%
Newbuildings
Related Party Transaction [Line Items]
Impairment	[2]	$ (696,000,000)	0
Total, by property, plant, and equipment disposals | Exploration and Production Equipment
Related Party Transaction [Line Items]
Loss on disposals		(245,000,000)	$ 0
Secretariat of the Federal Revenue Bureau of Brazil
Related Party Transaction [Line Items]
Income tax examination, estimate of possible loss		161,000,000
Nigeria
Related Party Transaction [Line Items]
Income tax examination, estimate of possible loss		$ 171,000,000
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".
[2]	As part of the Chapter 11 proceedings, the Debtors negotiated and announced a global settlement with various creditors, including Samsung Heavy Industries Co., Ltd. ("Samsung") and Daewoo Shipbuilding & Marine Engineering Co., Ltd ("DSME"). The global settlement included an agreement regarding the allowed claim of the newbuild shipyards Samsung and DSME, and the Debtors’ rejection and recognized termination of the newbuild contracts for the West Dorado, West Draco, West Aquila and the West Libra. As the Plan anticipates the rejection and termination of the newbuild contracts we have recognized an impairment of the newbuild assets related to the West Dorado, West Draco, West Aquila and the West Libra, totaling $696 million, in the year ended December 31, 2017.

Taxation - Income Tax Reconcili

Taxation - Income Tax Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income taxes at statutory rate	$ 0	$ 0	$ 0
Effect of change on uncertain tax positions relating to prior year	(5)	28	0
Effect of unremitted earnings of subsidiaries	3	(4)	38
Effect of taxable income in various countries	68	175	170
Total tax expense	$ 66	$ 199	$ 208

Taxation - Deferred Income Taxe

Taxation - Deferred Income Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets [Abstract]
Pensions and stock options	$ 4	$ 3
Provisions	49	28
Net operating losses carried forward	255	272
Other	0	2
Gross deferred tax assets	308	305
Valuation allowance	(230)	(245)
Deferred tax assets, net of valuation allowance	78	60
Deferred Tax Liability [Abstract]
Property, plant and equipment	138	126
Unremitted Earnings of Subsidiaries	37	34
Gross deferred tax liabilities	175	160
Net deferred tax (liability)/asset	$ (97)	$ (100)

Taxation - Changes to Uncertain

Taxation - Changes to Uncertain Tax Positions, Excluding Interest and Penalties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes to liabilities related to unrecognized tax benefits, excluding interest and penalties [Roll Forward]
Balance at the beginning of the period	$ 44	$ 9	$ 9
Increases as a result of positions taken in prior periods	23	35	0
Increases as a result of positions taken during the current period	0	2	0
Decreases as a result of positions taken in prior periods	(9)	(2)	0
Decreases as a result of positions taken in the current period	0	0	0
Decreases due to settlements	(3)	0	0
Balance at the end of the period	$ 55	$ 44	$ 9

Taxation - Earliest Open Tax Ye

Taxation - Earliest Open Tax Year (Details)	12 Months Ended
	Dec. 31, 2017
Angola
Income Tax Examination [Line Items]
Earliest Open Year	2,015
Nigeria
Income Tax Examination [Line Items]
Earliest Open Year	2,014
United States
Income Tax Examination [Line Items]
Earliest Open Year	2,014
Norway
Income Tax Examination [Line Items]
Earliest Open Year	2,013
Spain
Income Tax Examination [Line Items]
Earliest Open Year	2,008

Loss per share (Details)

Loss per share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net loss attributable to the parent		$ (2,973)	$ (181)	$ (634)
Less: Allocation to participating securities		0	0	0
Net loss attributable to the parent		(2,973)	(181)	(634)
Effect of dilution		0	0	0
Diluted net loss available to stockholders		$ (2,973)	$ (181)	$ (634)
Basic earnings per share:
Weighted average number of common shares outstanding (in shares)		505	501	493
Diluted earnings per share:
Weighted average number of common shares outstanding (in shares)		0	0	0
Effect of dilutive share options (in shares)	[1]	0	0	0
Weighted average number of common shares outstanding adjusted for the effects of dilution (in shares)		505	501	493
Basic loss per share (in dollars per share)		$ (5.89)	$ (0.36)	$ (1.29)
Diluted loss per share (in dollars per share)		$ (5.89)	$ (0.36)	$ (1.29)
Plan of reorganization, equity securities issued or to be issued, ownership percentage		2.00%
[1]	Certain stock options have been excluded from the calculation of diluted EPS because their exercise price exceeded our average share price during the calculation period.

Disposals of businesses and 109

Disposals of businesses and deconsolidation of subsidiaries - Disposal of the West Polaris (Details)		Jun. 19, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2017USD ($)business_disposal	Dec. 31, 2016USD ($)business_disposal	Dec. 31, 2015USD ($)		Feb. 29, 2016USD ($)	Jan. 01, 2016USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of disposals and deconsolidated subsidiaries | business_disposal				0	0
Contingent consideration realized	[1]			$ 27,000,000	$ 21,000,000	$ 47,000,000	[2]
Loss on disposal	[1]			(245,000,000)	$ 0	$ (63,000,000)
West Polaris earn out realized
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Enterprise value		$ 540,000,000
Debt assumed		336,000,000
Fair value of consideration received		235,000,000
Cash		204,000,000
Plus: Working capital adjustment		31,000,000
Seller’s credit recognized		$ 50,000,000
Interest rate related to sellers line of credit (as percent)		6.50%
Period after contract completion for potential reduction in receivable		3 years
Threshold for operating day rate		$ 450,000						$ 653,000	$ 490,000
Percentage above threshold for operating day rate (as percent)		50.00%
Contingent consideration realized			$ 32,000,000	$ 13,000,000
Loss on disposal		$ (77,000,000)
Disposal group, goodwill		$ 41,000,000
Seadrill Operating LP
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as percent)		42.00%
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".
[2]	Text selection found with no content.

Disposals of businesses and 110

Disposals of businesses and deconsolidation of subsidiaries - West Polaris Consideration (Details) - USD ($)		Jun. 19, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal	[1]		$ (245,000,000)	$ 0	$ (63,000,000)
West Polaris earn out realized
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Enterprise value		$ 540,000,000
Less: Debt assumed		(336,000,000)
Purchase price		204,000,000
Plus: Working capital adjustment		31,000,000
Purchase price		235,000,000
Cash		204,000,000
Less: net carrying value of assets and liabilities		(271,000,000)
Less: allocated goodwill to subsidiaries		(41,000,000)
Loss on disposal		$ (77,000,000)
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

Disposals of businesses and 111

Disposals of businesses and deconsolidation of subsidiaries - SeaMex Limited Narrative (Details) - USD ($)		Mar. 10, 2015	Sep. 30, 2016	Sep. 30, 2015	Jul. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 09, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale	[1]					$ (245,000,000)	$ 0	$ (63,000,000)
SeaMex Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Fair value of consideration received		$ 1,077,000,000
Net cash received		586,000,000
Seller’s credit recognized		250,000,000
Short term related party receivable		91,000,000
Direct repayment of debt by the JV on behalf of Seadrill		150,000,000
Consideration receivable		162,000,000			$ 162,000,000
Gain on sale		181,000,000
Loss on disposal		$ (49,000,000)
SeaMex Limited | Subsidiaries
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Management fee (as percent)						8.00%
SeaMex Limited | LIBOR
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest rate related to sellers line of credit (as percent)		6.50%
SeaMex Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest prior to disposal (as percent)									100.00%
Written notice period						120 days
SeaMex Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Third party ownership interest (as percent)		50.00%						50.00%
Ownership interest (as percent)		50.00%				50.00%	50.00%	50.00%	100.00%
Property, Plant and Equipment | Seadrill Partners LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Decrease in basis difference			$ 567,000,000	$ 427,000,000		$ 246,000,000
Remaining basis difference						1,000,000
Goodwill | Seadrill Partners LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining basis difference						$ 6,000,000
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

Disposals of businesses and 112

Disposals of businesses and deconsolidation of subsidiaries - SeaMex Limited Gain on Disposal (Details) - USD ($)		Mar. 10, 2015	Jul. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 09, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total non-current assets				$ 126,000,000	$ 128,000,000
Total assets				126,000,000	128,000,000
Gain on sale	[1]			$ (245,000,000)	$ 0	$ (63,000,000)
SeaMex Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as percent)		50.00%		50.00%	50.00%	50.00%	100.00%
SeaMex Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net cash consideration received		$ 749,000,000
Seller’s credit recognized		250,000,000
Direct repayment of debt by the JV on behalf of Seadrill		150,000,000
Consideration receivable in respect of West Titania		162,000,000	$ 162,000,000
Other related party balances payable		(71,000,000)
Cash paid to acquire 50% interest in the JV		(163,000,000)
Fair value of consideration received		1,077,000,000
Fair value of retained 50% investment in Seamex Limited		163,000,000
Cash and cash equivalents		40,000,000
Deferred tax assets - short term		8,000,000
Other current assets		20,000,000
Total current assets		68,000,000
Drilling units		969,000,000
Deferred tax asset - long term		4,000,000
Other non-current assets		86,000,000
Goodwill		49,000,000
Total non-current assets		1,108,000,000
Total assets		1,176,000,000
Trade accounts payable		(1,000,000)
Other current liabilities		(56,000,000)
Total current liabilities		(57,000,000)
Other non-current liabilities		(60,000,000)
Total non-current liabilities		(60,000,000)
Total liabilities		(117,000,000)
Carrying value of net assets		1,059,000,000
Gain on sale		$ 181,000,000
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

Restricted cash (Details)

Restricted cash (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash [Line Items]
Short-term restricted cash	$ 104	$ 75
Total restricted cash	104	75
Long-term restricted cash	0	0
Danske guarantee agreement
Restricted Cash [Line Items]
Short-term restricted cash	70	70
Cash pledged as collateral
Restricted Cash [Line Items]
Short-term restricted cash	6	0
Tax withholding deposits
Restricted Cash [Line Items]
Short-term restricted cash	5	5
Other
Restricted Cash [Line Items]
Short-term restricted cash	$ 23	$ 0

Marketable securities - Carryin

Marketable securities - Carrying Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (Loss) on Investments [Line Items]
Gross realized gains	$ 0	$ 0	$ 0
Amortized cost	93	93
Cumulative unrealized fair value gains	31	17
Carrying value	124	110
Archer Limited (Archer)
Gain (Loss) on Investments [Line Items]
Gross realized gains	0
Seadrill Partners LLC
Gain (Loss) on Investments [Line Items]
Amortized cost	93	93
Cumulative unrealized fair value gains	3	17
Carrying value	96	110
SapuraKencana
Gain (Loss) on Investments [Line Items]
Gross realized gains		$ 0	0
Carrying value			$ 195
Equity securities | Archer Limited (Archer)
Gain (Loss) on Investments [Line Items]
Amortized cost	0
Cumulative unrealized fair value gains	28
Carrying value	$ 28

Marketable securities - Changes

Marketable securities - Changes in Carrying Amounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (Loss) on Investments [Line Items]
Gross realized gains	$ 0	$ 0	$ 0
Gross realized losses	0	0	0
Gross unrealized gains	50	69	16
Gross unrealized losses	(36)	(52)	(476)
Gross proceeds from sales	0	195	0	[1]
Recognition and purchases	0	0	0
Gain/(loss) reclassified into income	0	(153)	(752)
Archer Limited (Archer)
Gain (Loss) on Investments [Line Items]
Gross realized gains	0
Gross realized losses	0
Gross unrealized gains	42
Gross unrealized losses	(14)
Gross proceeds from sales	0
Recognition and purchases	0
Gain/(loss) reclassified into income	0
Seadrill Partners - Common Units
Gain (Loss) on Investments [Line Items]
Gross realized gains	0	0	0
Gross realized losses	0	0	0
Gross unrealized gains	8	69	16
Gross unrealized losses	(22)	(52)	(346)
Gross proceeds from sales	0	0	0
Recognition and purchases	0	0	0
Gain/(loss) reclassified into income	$ 0	(153)	(574)
SapuraKencana
Gain (Loss) on Investments [Line Items]
Gross realized gains		0	0
Gross realized losses		0	0
Gross unrealized gains		0	0
Gross unrealized losses		0	(130)
Gross proceeds from sales		195	0
Recognition and purchases		0	0
Gain/(loss) reclassified into income		$ 0	$ (178)
[1]	Text selection found with no content.

Marketable securities - Narrati

Marketable securities - Narrative (Details)		Apr. 27, 2016USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)$ / shares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)		Dec. 31, 2017kr / shares	Apr. 30, 2017USD ($)	Apr. 25, 2017	Jun. 30, 2015$ / shares
Gain (Loss) on Investments [Line Items]
Marketable securities					$ 124,000,000	$ 110,000,000
Loss on impairment of investments					841,000,000	895,000,000	$ 1,285,000,000	[1]
Total impairment of marketable securities investments (reclassification from OCI)					0	153,000,000	752,000,000
Cumulative unrealized fair value gains					31,000,000	17,000,000
Share price | $ / shares				$ 5.90								$ 10.34
Restatement Adjustment | Other adjustments
Gain (Loss) on Investments [Line Items]
Loss on impairment of investments	[1]						11,000,000
SapuraKencana
Gain (Loss) on Investments [Line Items]
Impairment charge							167,000,000
Marketable securities							195,000,000
Total impairment of marketable securities investments (reclassification from OCI)				$ 167,000,000	0	0	$ 178,000,000
Proceeds from available-for-sale securities		$ 195,000,000
Seadrill Partners LLC
Gain (Loss) on Investments [Line Items]
Marketable securities					96,000,000	110,000,000
Cumulative unrealized fair value gains					$ 3,000,000	$ 17,000,000
Seadrill Partners LLC | Reclassification out of Accumulated Other Comprehensive Income
Gain (Loss) on Investments [Line Items]
Total impairment of marketable securities investments (reclassification from OCI)			$ (153,000,000)	$ 574,000,000
Archer Limited (Archer)
Gain (Loss) on Investments [Line Items]
Ownership interest (as percent)					15.69%	39.72%	39.90%				31.89%
Available-for-sale securities										$ 0
Available-for-sale equity securities, accumulated gain										$ 10,000,000
Gain on realization of marketable securities					$ 28,000,000
Share price | kr / shares									kr 10.05
[1]	Text selection found with no content.

Accounts receivable (Details)

Accounts receivable (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts Receivable, Net, Current [Abstract]
Allowance for doubtful accounts receivables	$ 35,000,000	$ 31,000,000	$ 39,000,000
Bad debt expense	$ 0	$ 0	$ 0

Other current assets (Details)

Other current assets (Details) - USD ($) $ in Millions		Mar. 13, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	[3]	Apr. 30, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Prepaid expenses			$ 87	$ 21
Deferred consideration	[1]		80	135
Taxes receivable			24	25
Reimbursable amounts due from customers			15	21
Deferred mobilization cost			15	35
Receivable from ship-yard	[2]		0	170
Other current assets			36	88
Total other current assets			257	495
Payments received from loans granted to related parties			$ 66	283	$ 233
Monthly repayment amount of non-contingent deferred consideration				5
Tender Rig Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-contingent deferred consideration							$ 145
Payments received from loans granted to related parties				10
Proceeds from interest received				$ 25
LIBOR | Tender Rig Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loan receivable basis spread on variable rate (as percent)							5.00%
Exploration and Production Equipment | Cancellation of West Mira
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Newbuilding settlement claim		$ 170
[1]	On April 30, 2013, we completed the disposal of the tender rig business to SapuraKencana. The total consideration consisted of a non-contingent deferred consideration of $145 million, bearing interest at LIBOR plus 5%, which was due in April 2016. During the year ended December 31, 2016, SapuraKencana repaid $10 million of the principal and paid $25 million of interest. On August 28, 2017 this was converted into a formalized loan agreement whereby $5 million is repaid each month, with the residual due to be repaid on August 3, 2018. We expect the entire amount will be recoverable.
[2]	The receivable from shipyard relates to the West Mira, which reached settlement for $170 million on March 13, 2017. For details on the arbitration process and subsequent settlement, refer to Note 6 "Loss on disposals" for more information.
[3]	Text selection found with no content.

Investment in associated com119

Investment in associated companies - Ownership Percentage (Details)	Dec. 31, 2017	Apr. 25, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 10, 2015	Mar. 09, 2015
Archer Limited (Archer)
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)	15.69%	31.89%	39.72%	39.90%
Seabras Sapura Participacoes Ltda (Seabras Sapura Participacoes)
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)	50.00%		50.00%	50.00%
Seabras Sapura Holding GmbH (Seabras Sapura Holding)
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)	50.00%		50.00%	50.00%
Itaunas Drilling B.V. (Itaunas Drilling)
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)	30.00%		30.00%	30.00%
Camburi Drilling B.V. (Camburi Drilling)
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)	30.00%		30.00%	30.00%
Sahy Drilling B.V. (Sahy Drilling)
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)	30.00%		30.00%	30.00%
SeaMex Ltd. (SeaMex)
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)	50.00%		50.00%	50.00%	50.00%	100.00%

Investment in associated com120

Investment in associated companies - Book Value (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Investment in associated companies		$ 1,473	$ 2,168
Investment in associated companies		1,473	2,168
Archer Limited (Archer)
Schedule of Equity Method Investments [Line Items]
Investment in associated companies	[1]		0
Seabras Sapura Participacoes
Schedule of Equity Method Investments [Line Items]
Investment in associated companies		63	47
Seabras Sapura Holding
Schedule of Equity Method Investments [Line Items]
Investment in associated companies		290	227
Itaunas Drilling
Schedule of Equity Method Investments [Line Items]
Investment in associated companies		0	0
Camburi Drilling
Schedule of Equity Method Investments [Line Items]
Investment in associated companies		0	0
Sahy Drilling
Schedule of Equity Method Investments [Line Items]
Investment in associated companies		0	0
Seadrill Partners LLC | Direct Ownership Interest
Schedule of Equity Method Investments [Line Items]
Investment in associated companies		857	1,537
Seadrill Partners LLC | Subordinated Units
Schedule of Equity Method Investments [Line Items]
Investment in associated companies		97	157
Seadrill Partners LLC | Member Interest and Incentive Distribution Rights
Schedule of Equity Method Investments [Line Items]
Investment in associated companies	[2]	64	64
SeaMex Limited
Schedule of Equity Method Investments [Line Items]
Investment in associated companies		$ 102	$ 136
[1]	In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized it as an available-for-sale security.
[2]	The Seadrill Partners - Seadrill member interest and Incentive Distribution Rights (“IDR’s”) are accounted for as cost-method investments on the basis that they do not represent common stock interests and their fair value is not readily determinable. The investments are held at cost and not subsequently re-measured. For more details on the deconsolidation of Seadrill Partners see Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information.

Investment in associated com121

Investment in associated companies - Narrative (Details)		Dec. 05, 2016USD ($)	Feb. 08, 2013USD ($)shares	Sep. 30, 2016USD ($)	Dec. 31, 2017USD ($)class_of_stockvesselclass_of_membership_interest	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Apr. 30, 2017USD ($)	Apr. 25, 2017	Jun. 19, 2015	Mar. 10, 2015	Mar. 09, 2015	Nov. 12, 2012USD ($)
Schedule of Equity Method Investments [Line Items]
Notional amount of investments acquired	[1]					$ 6,000,000
Total impairment of investments					$ 841,000,000	895,000,000	$ 1,285,000,000
Share in results from associated companies (net of tax)					$ 174,000,000	$ 283,000,000	192,000,000
JV partner investment to retain share in JV							$ 19,000,000
Seadrill Operating LP
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					42.00%
Seadrill Capricorn Holdings LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					49.00%
Number of classes of membership interest representing voting common stock | class_of_membership_interest					1
SFL Deepwater Limited
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					39.00%
Seadrill Mobile Units (Nigeria) Ltd
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					49.00%
Number of classes of stock representing voting common stock | class_of_stock					1
Archer Limited (Archer) | Loans Payable
Schedule of Equity Method Investments [Line Items]
Debt, face amount			$ 43,000,000
Equity Method Investee | Archer Limited (Archer)
Schedule of Equity Method Investments [Line Items]
Loan to related party													$ 55,000,000
Ownership interest (as percent)							39.89%
Archer Limited (Archer)
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					15.69%	39.72%	39.90%		31.89%
Available-for-sale securities								$ 0
Available-for-sale equity securities, accumulated gain								$ 10,000,000
Archer Limited (Archer) | Private Placement
Schedule of Equity Method Investments [Line Items]
New shares issued by equity method investment (in shares) | shares			82,003,000
Consideration received from shares issued			$ 98,000,000
Archer Limited (Archer) | Underwrite Placement
Schedule of Equity Method Investments [Line Items]
New shares issued by equity method investment (in shares) | shares			2,811,793
Consideration received from shares issued			$ 3,000,000
Seabras Sapura Participacoes
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					50.00%	50.00%	50.00%
Number of pipelying vessels | vessel					1
Ownership percentage held by equity method investee (as percent)					50.00%
Seabras Sapura Holding
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					50.00%	50.00%	50.00%
Number of pipelying vessels | vessel					5
Ownership percentage held by equity method investee (as percent)					50.00%
Itaunas Drilling, Camburi Drilling, and Sahy Drilling
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					30.00%
Ownership percentage held by equity method investee (as percent)					70.00%
Total impairment of investments					$ 0	$ 13,000,000	$ 0
Itaunas Drilling
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					30.00%	30.00%	30.00%
Ownership percentage held by equity method investee (as percent)					70.00%
Camburi Drilling
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					30.00%	30.00%	30.00%
Ownership percentage held by equity method investee (as percent)					70.00%
Sahy Drilling
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					30.00%	30.00%	30.00%
Ownership percentage held by equity method investee (as percent)					70.00%
Seadrill Mobile Units (Nigeria) Ltd
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)		51.00%
Seadrill Mobile Units (Nigeria) Ltd | Seadrill UK Ltd
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)		49.00%
Interest acquired (as percent)		10.00%
Notional amount of investments acquired		$ 6,600,000
Seadrill Mobile Units (Nigeria) Ltd | HHL
Schedule of Equity Method Investments [Line Items]
Notional amount of investments acquired		6,600,000
SeaMex Limited
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)					50.00%	50.00%	50.00%				50.00%	100.00%
Total impairment of investments				$ 76,000,000	$ 36,000,000	$ 76,000,000	$ 0
Third party ownership interest (as percent)							50.00%				50.00%
Seadrill Operating LP
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)										42.00%
Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Notional amount of investments acquired		$ 6,600,000
Total impairment of investments				$ 73,000,000	805,000,000	653,000,000	$ 533,000,000
Seadrill Partners, Seamex Limited and Itaunas Drilling, Camburi Drilling, and Sahy Drilling
Schedule of Equity Method Investments [Line Items]
Total impairment of investments					$ 841,000,000	$ 742,000,000	$ 533,000,000
[1]	uring the year ended December 31, 2016, certain consolidated VIEs of ours withdrew bank loans and made loans to the related party Ship Finance International. These balances are presented net in the consolidated statement of cash flows. Refer to Note 22 "Long-term debt" for further information.

Investment in associated com122

Investment in associated companies - Financial Information of Equity Method Investees (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Current assets	$ 1,975	$ 2,155
Non-current assets	7,983	9,145
Current liabilities	1,441	1,781
Non-current liabilities	4,964	6,278
Non-Controlling interest	1,398	1,343
Archer Limited (Archer)
Schedule of Equity Method Investments [Line Items]
Current assets		287
Non-current assets		773
Current liabilities		313
Non-current liabilities		718
Non-Controlling interest		0
Seabras Sapura Participacoes
Schedule of Equity Method Investments [Line Items]
Current assets	126	100
Non-current assets	299	317
Current liabilities	131	149
Non-current liabilities	169	174
Non-Controlling interest	0	0
Seabras Sapura Holding
Schedule of Equity Method Investments [Line Items]
Current assets	341	258
Non-current assets	1,331	1,393
Current liabilities	542	509
Non-current liabilities	845	988
Non-Controlling interest	0	0
Seadrill Partners
Schedule of Equity Method Investments [Line Items]
Current assets	1,214	1,214
Non-current assets	5,317	5,567
Current liabilities	546	665
Non-current liabilities	3,284	3,580
Non-Controlling interest	1,398	1,343.2
SeaMex Limited
Schedule of Equity Method Investments [Line Items]
Current assets	294	296
Non-current assets	1,036	1,095
Current liabilities	222	145
Non-current liabilities	666	818
Non-Controlling interest	$ 0	$ 0

Investment in associated com123

Investment in associated companies - Statement of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Operating revenues	$ 1,629	$ 3,087	$ 3,478
Net operating income	788	1,097	989
Net income	410	544	205
Net income attributable to non-controlling interest	94	265	231
Archer Limited (Archer)
Schedule of Equity Method Investments [Line Items]
Operating revenues		818	1,321
Net operating income		(41)	(13)
Net income		(166)	(359)
Net income attributable to non-controlling interest	0	0	0
Seabras Sapura Participacoes
Schedule of Equity Method Investments [Line Items]
Operating revenues	76	148	53
Net operating income	60	46	3
Net income	34	39	1
Net income attributable to non-controlling interest	0	0	0
Seabras Sapura Holding
Schedule of Equity Method Investments [Line Items]
Operating revenues	186	241	124
Net operating income	184	155	76
Net income	126	89	51
Net income attributable to non-controlling interest	0	0	0
Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Operating revenues	1,128	1,600	1,742
Net operating income	464	818	844
Net income	235	546	488
Net income attributable to non-controlling interest	94	265	231
SeaMex Limited
Schedule of Equity Method Investments [Line Items]
Operating revenues	239	280	238
Net operating income	80	119	79
Net income	15	36	24
Net income attributable to non-controlling interest	$ 0	$ 0	$ 0

Investment in associated com124

Investment in associated companies - Recorded Equity in Statutory Accounts (Details) - USD ($) $ in Millions		Dec. 31, 2017	Apr. 25, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 10, 2015	Mar. 09, 2015
Schedule of Equity Method Investments [Line Items]
Equity in statutory accounts		$ 427		$ 357	$ 322
Non-Controlling interest		$ 1,398		1,343
Archer Limited (Archer)
Schedule of Equity Method Investments [Line Items]
Equity in statutory accounts	[1]			15	$ 79
Non-Controlling interest				$ 0
Ownership interest (as percent)		15.69%	31.89%	39.72%	39.90%
Seabras Sapura Participacoes
Schedule of Equity Method Investments [Line Items]
Equity in statutory accounts		$ 63		$ 47	$ 24
Non-Controlling interest		$ 0		$ 0
Ownership interest (as percent)		50.00%		50.00%	50.00%
Seabras Sapura Holding
Schedule of Equity Method Investments [Line Items]
Equity in statutory accounts		$ 143		$ 77	$ 19
Non-Controlling interest		$ 0		$ 0
Ownership interest (as percent)		50.00%		50.00%	50.00%
Itaunas Drilling
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)		30.00%		30.00%	30.00%
Camburi Drilling
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)		30.00%		30.00%	30.00%
Sahy Drilling
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)		30.00%		30.00%	30.00%
Seadrill Partners LLC
Schedule of Equity Method Investments [Line Items]
Non-Controlling interest		$ 1,398		$ 1,343.2
Equity method investment, summarized financial information, equity before noncontrolling interest		$ 1,304		1,193
Seadrill Partners LLC | Subordinated Units
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)		18.00%
SeaMex Limited
Schedule of Equity Method Investments [Line Items]
Equity in statutory accounts		$ 221		218	$ 200
Non-Controlling interest		$ 0		$ 0
Ownership interest (as percent)		50.00%		50.00%	50.00%	50.00%	100.00%
[1]	In April 2017, following two shares issuances from Archer, we concluded that we no longer had significant influence over Archer's financial and operating decisions, and therefore derecognized our investment in associate and recognized as an available-for-sale security.

Newbuildings (Details)

Newbuildings (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Newbuildings [Roll Forward]
Opening balance		$ 15,807
Closing balance		13,464	$ 15,807
Loss on impairment of long lived assets		696	44	$ 563	[1]
West Dorado, West Draco, West Aquila and West Libra
Movement in Newbuildings [Roll Forward]
Loss on impairment of long lived assets		696
Newbuildings
Movement in Newbuildings [Roll Forward]
Opening balance		1,531	1,479
Additions		5	12
Capitalized interest and loan related costs		28	40
Disposals	[2]	(620)	0
Impairment	[3]	(696)	0
Closing balance		$ 248	$ 1,531	$ 1,479
[1]	Text selection found with no content.
[2]	In July 2017, Sevan Drilling and Cosco reached agreement to defer the Sevan Developer delivery period until June 30, 2020. The contract amendment included a termination clause for Cosco and therefore it was deemed that Sevan had lost control of the asset. The Newbuild asset and corresponding construction obligation were derecognized. Refer to Note 6 - Loss on disposals for further informati
[3]	As part of the Chapter 11 proceedings, the Debtors negotiated and announced a global settlement with various creditors, including Samsung Heavy Industries Co., Ltd. ("Samsung") and Daewoo Shipbuilding & Marine Engineering Co., Ltd ("DSME"). The global settlement included an agreement regarding the allowed claim of the newbuild shipyards Samsung and DSME, and the Debtors’ rejection and recognized termination of the newbuild contracts for the West Dorado, West Draco, West Aquila and the West Libra. As the Plan anticipates the rejection and termination of the newbuild contracts we have recognized an impairment of the newbuild assets related to the West Dorado, West Draco, West Aquila and the West Libra, totaling $696 million, in the year ended December 31, 2017.

Drilling units (Details)

Drilling units (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Drilling units [Line Items]
Net book value	$ 13,464	$ 15,807
Drilling units
Drilling units [Line Items]
Cost	17,335	17,753
Accumulated depreciation	(4,119)	(3,477)
Net book value	$ 13,216	$ 14,276

Drilling units - Narrative (Det

Drilling units - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Drilling units
Drilling units [Line Items]
Depreciation and amortization expense	$ 779	$ 801	$ 761

Equipment (Details)

Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Net book value	$ 13,464	$ 15,807
Equipment
Property, Plant and Equipment [Line Items]
Cost	84	77
Accumulated depreciation	(55)	(36)
Net book value	29	41
Depreciation and amortization expense	$ 19	$ 9	$ 18

Goodwill and other intangibl129

Goodwill and other intangible assets and liabilities - Goodwill Rollforward (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill		$ 795	$ 795
Accumulated impairment losses		(795)	(795)
Total opening goodwill		0	0
Disposals of businesses and deconsolidation of subsidiaries (Note 11)		0	0
Loss on impairment of goodwill	$ 563	0	0
Goodwill		795	795
Accumulated impairment losses		(795)	(795)
Total closing goodwill		$ 0	$ 0

Goodwill and other intangibl130

Goodwill and other intangible assets and liabilities - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2015
Goodwill [Line Items]
Share price, percentage decrease	43.00%
Share price	$ 5.90			$ 10.34
Share price, weighted average, percentage decrease	(34.00%)
Share price, weighted average	$ 7.96			$ 12.04
Loss on impairment of goodwill	$ 563	$ 0	$ 0
Remaining economic lives of underlying assets			30 years
Weighted average cost of capital (as percent)			10.00%
Lower range of amortization life of unfavorable contracts		2 years
Upper range of amortization life of unfavorable contracts		5 years
Amortization life of unfavorable contracts		5 years
Noncontrolling Interest | Floaters
Goodwill [Line Items]
Loss on impairment of goodwill	$ 95

Goodwill and other intangibl131

Goodwill and other intangible assets and liabilities - Gross Carrying Amounts and Amortization (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-lived Intangible Liabilities [Roll Forward]
Gross carrying amount, beginning balance	$ 444	$ 444
Accumulated amortization, beginning balance	(378)	(313)
Net carrying amount, beginning balance	66	131
Amortization of unfavorable contracts	(43)	(65)
Gross carrying amount, ending balance	444	444
Accumulated amortization, ending balance	(421)	(378)
Net carrying amount, ending balance	$ 23	$ 66

Goodwill and other intangibl132

Goodwill and other intangible assets and liabilities - Amortization of Favorable and Unfavorable Contracts (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
2,018	$ 23
2,019	0
2,020	0
2,021	0
2,022	0
Total	$ 23	$ 66	$ 131

Other non-current assets (Detai

Other non-current assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Assets, Noncurrent Disclosure [Abstract]
Deferred tax effect of internal transfer of assets	$ 75	$ 84
Deferred mobilization costs	5	14
Other	1	3
Total other non-current assets	$ 81	$ 101

Long-term debt - Schedule of De

Long-term debt - Schedule of Debt (Details)	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2017SEK (kr)	Dec. 31, 2017NOK (kr)	Jul. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Aug. 31, 2015USD ($)	Jan. 31, 2015USD ($)	Sep. 30, 2013USD ($)	Jul. 31, 2013USD ($)	Apr. 30, 2013USD ($)	Mar. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Sep. 30, 2012USD ($)	Dec. 31, 2011USD ($)
Debt Instrument [Line Items]
Protection payments	$ 81,000,000
Total debt principal	8,701,000,000				$ 9,608,000,000
Less: Debt balance held as subject to compromise	(7,705,000,000)				0
Debt balance not subject to compromise	996,000,000				9,608,000,000
Less: current interest bearing debt not subject to compromise	(511,000,000)				(3,230,000,000)
Long-term interest bearing debt not subject to compromise	485,000,000				6,378,000,000
Unamortized debt issuance costs	66,000,000
Secured Debt
Debt Instrument [Line Items]
Total debt principal	5,581,000,000				6,450,000,000
Unsecured bonds
Debt Instrument [Line Items]
Less: Debt balance held as subject to compromise	(5,371,000,000)
$1,500 million facility | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	1,500,000,000
Total debt principal	1,112,000,000				1,219,000,000
$1,350 million facility | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	1,350,000,000
Total debt principal	931,000,000				1,046,000,000
$2,000 million facility (NADL) | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	2,000,000,000
Total debt principal	897,000,000				1,033,000,000
$1,750 million facility (Sevan Drilling)
Debt Instrument [Line Items]
Debt, face amount								$ 1,750,000,000
$1,750 million facility (Sevan Drilling) | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	1,750,000,000
Total debt principal	856,000,000				945,000,000
$950 million facility | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	950,000,000						$ 950,000,000
Total debt principal	558,000,000				622,000,000
$1,450 million facility | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	1,450,000,000										$ 1,450,000,000
Total debt principal	318,000,000				353,000,000
$450 million Eminence facility | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	450,000,000
Total debt principal	261,000,000				278,000,000
$360 facility (Asia Offshore Drilling) | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	360,000,000									$ 360,000,000
Total debt principal	210,000,000				237,000,000
$300 million facility | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	300,000,000								$ 300,000,000
Total debt principal	142,000,000				162,000,000
$400 million facility | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	400,000,000			$ 400,000,000										$ 400,000,000
Total debt principal	133,000,000				190,000,000
$450 million facility (2015) | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	450,000,000					$ 450,000,000
Total debt principal	101,000,000				175,000,000
$440 million facility | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	440,000,000			$ 440,000,000								$ 440,000,000
Total debt principal	62,000,000				190,000,000
Credit facility, Ship Finance International Loans, Total [Member] | Secured Debt
Debt Instrument [Line Items]
Total debt principal	786,000,000				883,000,000
$390 million facility (SFL Deepwater) | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	390,000,000
Total debt principal	226,000,000				248,000,000
$375 million facility (SFL Hercules) | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	375,000,000
$475 million facility (SFL Linus) | Secured Debt
Debt Instrument [Line Items]
Debt, face amount	475,000,000
Total debt principal	309,000,000				356,000,000
Total unsecured bonds | Unsecured bonds
Debt Instrument [Line Items]
Total debt principal	2,334,000,000				2,275,000,000
$1,000 million bond | Unsecured bonds
Debt Instrument [Line Items]
Debt, face amount	1,000,000,000												$ 1,000,000,000
Total debt principal	843,000,000				843,000,000
NOK1,800 million bond | Unsecured bonds
Debt Instrument [Line Items]
Debt, face amount | kr			kr 1,800,000,000
Total debt principal	231,000,000				210,000,000
$500 million bond | Unsecured bonds
Debt Instrument [Line Items]
Debt, face amount	500,000,000
Total debt principal	479,000,000				479,000,000
NOK1,500 million bond (NADL) | Unsecured bonds
Debt Instrument [Line Items]
Debt, face amount | kr			kr 1,500,000,000
Total debt principal	182,000,000				165,000,000
$ 600 million bond (NADL) | Unsecured bonds
Debt Instrument [Line Items]
Debt, face amount	600,000,000
Total debt principal	413,000,000				413,000,000
SEK 1,500 million bond | Unsecured bonds
Debt Instrument [Line Items]
Debt, face amount | kr		kr 1,500,000,000
Total debt principal	$ 186,000,000				$ 165,000,000

Long-term debt - Outstanding De

Long-term debt - Outstanding Debt, Long-term and Debt Issuance Costs (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Principal outstanding
Principal outstanding, current portion of long-term debt	$ 511	$ 3,230
Principal outstanding, noncurrent portion	485	6,378
Debt held as subject to compromise	7,705	0
Total debt principal	8,701	9,608
Less: Debt issuance costs
Debt issuance costs, current portion of long-term debt	(2)	(35)
Debt issuance costs, noncurrent portion	0	(59)
Debt issuance costs, gross	(2)	(94)
Total debt
Total debt, current portion	509	3,195
Total debt, noncurrent portion	485	6,319
Total debt, net of debt issuance costs	$ 8,699	$ 9,514

Long-term debt - Debt Maturity

Long-term debt - Debt Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2,018	$ 511
2,019	485
Total debt principal	$ 996	$ 9,608

Long-term debt - Credit facilit

Long-term debt - Credit facilities subject to compromise (Details)

Apr. 28, 2016

Aug. 31, 2017USD ($)

May 31, 2017USD ($)

Jun. 30, 2016

Aug. 31, 2015USD ($)

Jan. 31, 2015USD ($)

Aug. 31, 2014USD ($)

Jul. 31, 2014USD ($)drilling_unit

Dec. 31, 2013USD ($)

Sep. 30, 2013USD ($)tranche

Jul. 31, 2013USD ($)

Apr. 30, 2013USD ($)tranche

Mar. 31, 2013USD ($)

Dec. 31, 2012USD ($)rig

Dec. 31, 2011USD ($)

Apr. 30, 2011USD ($)drilling_unit

Dec. 31, 2017USD ($)

Dec. 31, 2017USD ($)

Jul. 31, 2017USD ($)

Apr. 30, 2017USD ($)

Dec. 31, 2016USD ($)

Feb. 28, 2015USD ($)

Oct. 23, 2013USD ($)

Mar. 31, 2013NOK (kr)

Debt Instrument [Line Items]

Debt outstanding

$ 8,701,000,000

$ 8,701,000,000

$ 9,608,000,000

$2,000 million facility (NADL) | Secured Debt

Debt Instrument [Line Items]

Debt, face amount

$ 2,000,000,000

Remaining borrowing capacity

50,000,000

$ 50,000,000

Commitment fee (as percent)

40.00%

$2,000 million facility (NADL) | Secured Debt | LIBOR

Debt Instrument [Line Items]

Description of variable rate basis

LIBOR

Basis spread on variable rate (as percent)

2.00%

$440 million facility | Secured Debt | LIBOR

Debt Instrument [Line Items]

Description of variable rate basis

LIBOR

Basis spread on variable rate (as percent)

3.25%

US$101 Million Secured Credit Facility | Secured Debt

Debt Instrument [Line Items]

Debt, face amount

101,000,000

$ 101,000,000

US$98 Million Secured Credit Facility | Secured Debt

Debt Instrument [Line Items]

Debt, face amount

98,000,000

98,000,000

$1,450 million facility | Secured Debt

Debt Instrument [Line Items]

Debt covenant, collateral to outstanding loan value percentage (as percent)

125.00%

Debt collateral amount

615,000,000

615,000,000

$360 facility (Asia Offshore Drilling) | Tranche 1

Debt Instrument [Line Items]

Amount drawn from the facility

$ 120,000,000

$360 facility (Asia Offshore Drilling) | Tranche 2

Debt Instrument [Line Items]

Amount drawn from the facility

120,000,000

$360 facility (Asia Offshore Drilling) | Tranche 3

Debt Instrument [Line Items]

Amount drawn from the facility

120,000,000

$1,750 million facility (Sevan Drilling)

Debt Instrument [Line Items]

Debt, face amount

$ 1,750,000,000

Number of tranches | tranche

2

$1,750 million facility (Sevan Drilling) | Tranche 1

Debt Instrument [Line Items]

Debt, face amount

$ 1,400,000,000

Outstanding balance

$ 1,400,000,000

$1,750 million facility (Sevan Drilling) | Tranche 2

Debt Instrument [Line Items]

Debt, face amount

$ 350,000,000

$1,750 million facility (Sevan Drilling) | Sevan Driller

Debt Instrument [Line Items]

Debt collateral amount

525,000,000

525,000,000

$1,750 million facility (Sevan Drilling) | Sevan Brasil

Debt Instrument [Line Items]

Debt collateral amount

552,000,000

552,000,000

$1,750 million facility (Sevan Drilling) | Sevan Louisiana

Debt Instrument [Line Items]

Debt collateral amount

$ 648,000,000

$ 648,000,000

Credit Facility $1,500 - 2014 | Tranche 1

Debt Instrument [Line Items]

Debt instrument term

5 years

Debt outstanding

$ 300,000,000

Balloon payment to be paid

$ 175,000,000

Debt instrument, interest rate (as percent)

2.38%

Credit Facility $1,500 - 2014 | Tranche 2

Debt Instrument [Line Items]

Debt instrument term

5 years

Credit facility US $950 - West Carina

Debt Instrument [Line Items]

Debt instrument term

5 years

Balloon payment to be paid

$ 187,000,000

Debt instrument, interest rate (as percent)

2.12%

Credit facility US $950 - West Carina | LIBOR

Debt Instrument [Line Items]

Basis spread on variable rate (as percent)

2.00%

Credit facility US $950 - West Carina | ECA Facility

Debt Instrument [Line Items]

Debt instrument term

12 years

Profile period

12 years

Senior Notes | $450 million Eminence facility | Secured Debt

Debt Instrument [Line Items]

Basis spread on variable rate (as percent)

2.50%

Senior Unsecured Bond | NOK1,800 million bond

Debt Instrument [Line Items]

Debt, face amount | kr

kr 1,800,000,000

Debt instrument, interest rate (as percent)

4.94%

4.94%

$2,000 million facility (NADL)

Debt Instrument [Line Items]

Debt, face amount

$ 2,000,000,000

Number of drilling rigs in an acquisition | drilling_unit

6

Assets pledged

$ 1,810,000,000

$ 1,810,000,000

Debt instrument term

6 years

Payment due at maturity of debt

908,000,000

908,000,000

Secured Debt

Debt Instrument [Line Items]

Debt outstanding

5,581,000,000

5,581,000,000

6,450,000,000

Secured Debt | Credit facility US$700

Debt Instrument [Line Items]

Debt outstanding

0

0

Secured Debt | Credit facility, Ship Finance International Loans, $420 facility | Seadrill Partners LLC

Debt Instrument [Line Items]

Debt, face amount

420,000,000

420,000,000

Secured Debt | $2,000 million facility (NADL)

Debt Instrument [Line Items]

Debt, face amount

2,000,000,000

2,000,000,000

Debt outstanding

897,000,000

897,000,000

1,033,000,000

Debt covenant, collateral to outstanding loan value percentage (as percent)

135.00%

Secured Debt | $400 million facility

Debt Instrument [Line Items]

Debt, face amount

$ 400,000,000

400,000,000

400,000,000

$ 400,000,000

Assets pledged

507,000,000

507,000,000

Debt instrument term

5 years

Debt outstanding

133,000,000

133,000,000

190,000,000

Payment due at maturity of debt

135,000,000

135,000,000

Debt covenant, collateral to outstanding loan value percentage (as percent)

150.00%

Protection payment

2,000,000

Secured Debt | $400 million facility | Secured Debt | LIBOR

Debt Instrument [Line Items]

Description of variable rate basis

LIBOR

Basis spread on variable rate (as percent)

2.50%

Secured Debt | $400 million facility | Shelf Drilling

Debt Instrument [Line Items]

Repayments of debt

$ 47,000,000

Secured Debt | $440 million facility

Debt Instrument [Line Items]

Debt, face amount

$ 440,000,000

440,000,000

$ 440,000,000

440,000,000

Debt instrument term

5 years

Repayments of debt

$ 109,000,000

Debt outstanding

62,000,000

$ 62,000,000

190,000,000

Payment due at maturity of debt

64,000,000

64,000,000

Debt covenant, collateral to outstanding loan value percentage (as percent)

135.00%

Protection payment

2,000,000

Number of tender rigs in an acquisition | rig

2

Number of jack up drilling rigs in an acquisition | rig

2

Amount drawn from the facility

320,000,000

Debt collateral amount

188,000,000

188,000,000

Secured Debt | $1,450 million facility

Debt Instrument [Line Items]

Debt, face amount

$ 1,450,000,000

1,450,000,000

1,450,000,000

Debt outstanding

318,000,000

318,000,000

353,000,000

Secured Debt | $1,450 million facility | LIBOR

Debt Instrument [Line Items]

Description of variable rate basis

LIBOR

Secured Debt | $1,450 million facility | LIBOR | Minimum

Debt Instrument [Line Items]

Basis spread on variable rate (as percent)

2.70%

Secured Debt | $1,450 million facility | LIBOR | Maximum

Debt Instrument [Line Items]

Basis spread on variable rate (as percent)

3.00%

Secured Debt | $1,450 million facility | Tranche 1

Debt Instrument [Line Items]

Debt, face amount

$ 203,000,000

Secured Debt | $1,450 million facility | Seadrill Limited and Seadrill Partners LLC

Debt Instrument [Line Items]

Debt outstanding

318,000,000

318,000,000

695,000,000

Secured Debt | $360 facility (Asia Offshore Drilling)

Debt Instrument [Line Items]

Debt, face amount

$ 360,000,000

360,000,000

360,000,000

Debt instrument term

5 years

Debt outstanding

210,000,000

210,000,000

237,000,000

Debt covenant, collateral to outstanding loan value percentage (as percent)

120.00%

Number of tranches | tranche

3

Secured Debt | $360 facility (Asia Offshore Drilling) | LIBOR

Debt Instrument [Line Items]

Basis spread on variable rate (as percent)

2.75%

Secured Debt | $300 million facility

Debt Instrument [Line Items]

Debt, face amount

$ 300,000,000

300,000,000

300,000,000

Debt outstanding

142,000,000

142,000,000

162,000,000

Debt covenant, collateral to outstanding loan value percentage (as percent)

135.00%

Outstanding balance

142,000,000

$ 142,000,000

162,000,000

Commercial guarantee term

5 years

Secured Debt | $300 million facility | LIBOR

Debt Instrument [Line Items]

Description of variable rate basis

LIBOR

Basis spread on variable rate (as percent)

3.00%

Secured Debt | $300 million facility | Seadrill Tucana Ltd.

Debt Instrument [Line Items]

Assets pledged

181,000,000

$ 181,000,000

Secured Debt | $300 million facility | Seadrill Castor Ltd.

Debt Instrument [Line Items]

Assets pledged

186,000,000

186,000,000

Secured Debt | $1,750 million facility (Sevan Drilling)

Debt Instrument [Line Items]

Debt, face amount

1,750,000,000

1,750,000,000

Debt outstanding

856,000,000

856,000,000

945,000,000

Debt covenant, collateral to outstanding loan value percentage (as percent)

110.00%

Outstanding balance

856,000,000

856,000,000

945,000,000

Secured Debt | $1,750 million facility (Sevan Drilling) | LIBOR

Debt Instrument [Line Items]

Basis spread on variable rate (as percent)

2.85%

Secured Debt | $450 million Eminence facility

Debt Instrument [Line Items]

Debt, face amount

450,000,000

450,000,000

Assets pledged

508,000,000

508,000,000

Debt outstanding

261,000,000

261,000,000

278,000,000

Debt covenant, collateral to outstanding loan value percentage (as percent)

130.00%

Outstanding balance

261,000,000

261,000,000

278,000,000

Maximum borrowing capacity

$ 450,000,000

$ 450,000,000

Secured Debt | $450 million Eminence facility | LIBOR

Debt Instrument [Line Items]

Description of variable rate basis

LIBOR

Basis spread on variable rate (as percent)

2.50%

1.75%

Secured Debt | Credit Facility $1,500 - 2014

Debt Instrument [Line Items]

Debt, face amount

$ 1,500,000,000

Debt instrument term

12 years

Description of variable rate basis

LIBOR

Debt covenant, collateral to outstanding loan value percentage (as percent)

122.00%

Outstanding balance

1,112,000,000

$ 1,112,000,000

1,219,000,000

Debt collateral amount

$ 1,831,000,000

Number of newbuild jack-ups under finance lease arrangements | drilling_unit

3

Secured Debt | Credit Facility $1,500 - 2014 | Minimum

Debt Instrument [Line Items]

Basis spread on variable rate (as percent)

1.70%

Secured Debt | Credit Facility $1,500 - 2014 | Maximum

Debt Instrument [Line Items]

Basis spread on variable rate (as percent)

2.38%

Secured Debt | Credit Facility $1,350

Debt Instrument [Line Items]

Debt, face amount

$ 1,350,000,000

Debt instrument term

5 years

Debt covenant, collateral to outstanding loan value percentage (as percent)

120.00%

Debt collateral amount

1,570,000,000

$ 1,570,000,000

Secured Debt | Credit Facility $1,350 | LIBOR

Debt Instrument [Line Items]

Description of variable rate basis

LIBOR

Basis spread on variable rate (as percent)

2.00%

Secured Debt | Credit Facility $1,350 | Term Loan Facility

Debt Instrument [Line Items]

Debt outstanding

$ 675,000,000

Secured Debt | Credit Facility $1,350 | Revolving Credit Facility

Debt Instrument [Line Items]

Debt outstanding

$ 675,000,000

Secured Debt | $1,350 million facility

Debt Instrument [Line Items]

Debt, face amount

1,350,000,000

$ 1,350,000,000

Debt outstanding

931,000,000

931,000,000

1,046,000,000

Secured Debt | $950 million facility

Debt Instrument [Line Items]

Debt, face amount

$ 950,000,000

950,000,000

950,000,000

Debt outstanding

558,000,000

558,000,000

622,000,000

Remaining borrowing capacity

$ 171,000,000

Debt covenant, collateral to outstanding loan value percentage (as percent)

150.00%

120.00%

Debt collateral amount

1,256,000,000

1,256,000,000

Profile period

12 years

Secured Debt | Credit facility US $950 - West Carina

Debt Instrument [Line Items]

Debt, face amount

$ 60,000,000

Secured Debt | Credit facility US $950 - West Carina | ECA Facility

Debt Instrument [Line Items]

Debt, face amount

190,000,000

Secured Debt | Credit facility US $950 - West Eclipse

Debt Instrument [Line Items]

Debt, face amount

$ 225,000,000

Guarantee fee percentage (as percent)

1.30%

Secured Debt | $450 million facility (2015)

Debt Instrument [Line Items]

Debt, face amount

$ 450,000,000

450,000,000

450,000,000

Debt instrument term

5 years

Debt outstanding

101,000,000

101,000,000

$ 175,000,000

Remaining borrowing capacity

165,000,000

Debt collateral amount

$ 527,000,000

$ 527,000,000

Profile period

8 years 6 months

Secured Debt | $450 million facility (2015) | LIBOR

Debt Instrument [Line Items]

Basis spread on variable rate (as percent)

2.50%

Secured Debt | $450 million facility (2015) | Shelf Drilling

Debt Instrument [Line Items]

Repayments of debt

$ 54,000,000

Line of Credit | Credit facility US $950 - West Carina | Revolving Credit Facility

Debt Instrument [Line Items]

Debt, face amount

$ 250,000,000

Remaining borrowing capacity

71,000,000

Line of Credit | Credit facility US $950 - West Eclipse | Revolving Credit Facility

Debt Instrument [Line Items]

Debt, face amount

225,000,000

Remaining borrowing capacity

$ 100,000,000

Balloon payment to be paid

$ 225,000,000

Long-term debt - Credit faci138

Long-term debt - Credit facilities not subject to compromise (Details)	1 Months Ended
	Apr. 30, 2013USD ($)tranche	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Debt outstanding		$ 8,701,000,000	$ 9,608,000,000
Secured Debt
Debt Instrument [Line Items]
Debt outstanding		5,581,000,000	6,450,000,000
Secured Debt | $360 facility (Asia Offshore Drilling)
Debt Instrument [Line Items]
Debt, face amount	$ 360,000,000	360,000,000
Number of tranches | tranche	3
Debt instrument term	5 years
Debt outstanding		210,000,000	$ 237,000,000
Debt covenant, collateral to outstanding loan value percentage (as percent)	120.00%
Secured Debt | $360 facility (Asia Offshore Drilling) | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as percent)	2.75%
Secured Debt | Credit facility US$360 (Asia Offshore Drilling) AOD One
Debt Instrument [Line Items]
Debt collateral amount		210,000,000
Secured Debt | Credit facility US$360 (Asia Offshore Drilling) AOD Two
Debt Instrument [Line Items]
Debt collateral amount		201,000,000
Secured Debt | Credit facility US$360 (Asia Offshore Drilling) AOD Three
Debt Instrument [Line Items]
Debt collateral amount		$ 209,000,000
Tranche 1 | $360 facility (Asia Offshore Drilling)
Debt Instrument [Line Items]
Amount drawn from the facility	$ 120,000,000
Tranche 2 | $360 facility (Asia Offshore Drilling)
Debt Instrument [Line Items]
Amount drawn from the facility	120,000,000
Tranche 3 | $360 facility (Asia Offshore Drilling)
Debt Instrument [Line Items]
Amount drawn from the facility	$ 120,000,000

Long-term debt - Ship Finance I

Long-term debt - Ship Finance International Limited ("Ship Finance") Loans (Details) - USD ($)	1 Months Ended	12 Months Ended
	Oct. 31, 2013	Dec. 31, 2017	Dec. 31, 2016	Feb. 28, 2015	May 31, 2013
Debt Instrument [Line Items]
Debt outstanding		$ 8,701,000,000	$ 9,608,000,000
Secured Debt
Debt Instrument [Line Items]
Debt outstanding		5,581,000,000	6,450,000,000
Secured Debt | $375 million facility (SFL Hercules)
Debt Instrument [Line Items]
Debt, face amount		375,000,000
Secured Debt | $390 million facility (SFL Deepwater)
Debt Instrument [Line Items]
Debt, face amount		390,000,000
Debt outstanding		226,000,000	248,000,000
Secured Debt | $475 million facility (SFL Linus)
Debt Instrument [Line Items]
Debt, face amount		475,000,000
Debt outstanding		309,000,000	356,000,000
Credit facility, International Loans
Debt Instrument [Line Items]
Debt, face amount				$ 475,000,000
SFL Hercules Limited | Secured Debt | $375 million facility (SFL Hercules)
Debt Instrument [Line Items]
Debt, face amount					$ 375,000,000
Assets pledged		$ 508,000,000
Debt instrument term		6 years
Debt outstanding		$ 251,000,000	279,000,000
Remaining borrowing capacity		$ 0
SFL Hercules Limited | Secured Debt | $375 million facility (SFL Hercules) | LIBOR
Debt Instrument [Line Items]
Description of variable rate basis		LIBOR
Basis spread on variable rate (as percent)		2.75%
SFL Hercules Limited | Revolving Credit Facility | Secured Debt | $375 million facility (SFL Hercules)
Debt Instrument [Line Items]
Draw on credit facility		$ 50,000,000
West Taurus | Secured Debt | $390 million facility (SFL Deepwater)
Debt Instrument [Line Items]
Debt, face amount	$ 390,000,000
Assets pledged		$ 385,000,000
Debt instrument term		5 years
Remaining borrowing capacity		$ 0
West Taurus | Secured Debt | $390 million facility (SFL Deepwater) | LIBOR
Debt Instrument [Line Items]
Description of variable rate basis		LIBOR
Basis spread on variable rate (as percent)		2.50%
West Taurus | Revolving Credit Facility | Secured Debt | $390 million facility (SFL Deepwater)
Debt Instrument [Line Items]
Draw on credit facility		$ 50,000,000
SFL Linus Ltd | Secured Debt | $475 million facility (SFL Linus)
Debt Instrument [Line Items]
Debt, face amount	$ 475,000,000
Assets pledged		515,000,000
Draw on credit facility			$ 50,000,000
Remaining borrowing capacity		$ 0
SFL Linus Ltd | Secured Debt | $475 million facility (SFL Linus) | LIBOR
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Basis spread on variable rate (as percent)		2.75%

Long-term debt - Unsecured Bond

Long-term debt - Unsecured Bonds subject to compromise (Details)		Jun. 13, 2016USD ($)$ / sharesshares	May 20, 2016USD ($)$ / sharesshares	Jun. 30, 2016USD ($)$ / sharesshares	May 31, 2016USD ($)$ / sharesshares	Dec. 31, 2014USD ($)	Dec. 31, 2014NOK (kr)	Jun. 30, 2014USD ($)	Mar. 31, 2014SEK (kr)	Oct. 31, 2013NOK (kr)	Mar. 31, 2013NOK (kr)	Sep. 30, 2012USD ($)	May 31, 2014USD ($)	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)shares	Dec. 31, 2017SEK (kr)shares	Dec. 31, 2017NOK (kr)shares	Sep. 12, 2017shares	Jun. 29, 2016	May 30, 2016	Feb. 28, 2015NOK (kr)	Dec. 31, 2014NOK (kr)	Jan. 31, 2014USD ($)	Sep. 30, 2013USD ($)	May 10, 2005$ / sharesshares
Debt Instrument [Line Items]
Original amount of debt converted	[1]														$ 105,000,000
Debt outstanding														$ 8,701,000,000	9,608,000,000
Conversion of convertible bond															58,000,000
Net gain on debt extinguishment														$ 19,000,000	$ 47,000,000	$ 8,000,000
Number of shares issued (in shares) | shares															15,684,340
Common shares, par value (in dollars per share) | $ / shares				$ 2	$ 2									$ 2	$ 2											$ 2
Common stock, shares issued (in shares) | shares		508,444,280	500,944,280											508,763,020	508,763,020	493,078,680	508,763,020	508,763,020								6,000
Common shares, shares outstanding (in shares) | shares		508,444,280	500,944,280											504,518,940	504,444,280	492,759,940	504,518,940	504,518,940	508,763,020
Archer Limited (Archer)
Debt Instrument [Line Items]
Net gain on debt extinguishment														$ 19,000,000
Subordinated loan															$ 37,000,000
Loans payable															45,000,000
Loans payable fair value															56,000,000
Unsecured bonds | $1,000 million fixed interest bond
Debt Instrument [Line Items]
Debt, face amount												$ 1,000,000,000		1,000,000,000
Fixed interest rate (as percent)									6.125%			5.625%
Maturity date of debt												September 2,017
Debt outstanding														843,000,000	843,000,000
Net gain on debt extinguishment														47,000,000	8,000,000
Debt instrument term												5 years
Debt repurchased		$ 50,000,000	$ 55,000,000													$ 52,000,000
Number of shares issued (in shares) | shares		7,500,000	8,184,340
Common shares, par value (in dollars per share) | $ / shares		$ 2	$ 2
Common stock, shares issued (in shares) | shares		508,444,280	500,944,280
Unsecured debt outstanding														843,000,000	843,000,000
Unsecured bonds | NOK1,800 million bond
Debt Instrument [Line Items]
Debt, face amount | kr																		kr 1,800,000,000
Debt outstanding														231,000,000	210,000,000
Unsecured bonds | $500 million bond
Debt Instrument [Line Items]
Debt, face amount														500,000,000
Debt outstanding														479,000,000	479,000,000
Unsecured bonds | NOK1,500 million bond (NADL)
Debt Instrument [Line Items]
Debt, face amount | kr																		kr 1,500,000,000
Debt outstanding														182,000,000	165,000,000
Unsecured bonds | $ 600 million bond (NADL)
Debt Instrument [Line Items]
Debt, face amount														600,000,000
Debt outstanding														413,000,000	413,000,000
Unsecured bonds | SEK 1,500 million bond
Debt Instrument [Line Items]
Debt, face amount | kr																	kr 1,500,000,000
Debt outstanding														186,000,000	165,000,000
$1,000 million fixed interest bond
Debt Instrument [Line Items]
Fixed interest rate (as percent)				6.125%	6.125%							5.625%								5.625%	5.625%
Debt repurchased				$ 50,000,000	$ 55,000,000
Number of shares issued (in shares) | shares				7,500,000	8,184,340
Senior Unsecured Bond | NOK1,800 million bond
Debt Instrument [Line Items]
Debt, face amount | kr											kr 1,800,000,000
Unsecured debt outstanding														$ 231,000,000	210,000,000
Debt instrument, interest rate (as percent)														4.94%			4.94%	4.94%
Senior Unsecured Bond | NOK1,800 million bond | Norwegian Interbank Offered Rate (NIBOR)
Debt Instrument [Line Items]
Description of variable rate basis											NIBOR
Basis spread on variable rate (as percent)											3.75%
Senior Unsecured Bond | $500 million bond
Debt Instrument [Line Items]
Debt, face amount																									$ 500,000,000
Net gain on debt extinguishment						$ 3,000,000
Debt repurchased						$ 21,400,000
Unsecured debt outstanding														$ 479,000,000	479,000,000
Debt instrument, interest rate (as percent)									6.625%																6.125%
Percent of principal amount of debt owned						4.30%																	4.30%
Senior Unsecured Bond | NOK1,500 million bond (NADL)
Debt Instrument [Line Items]
Debt, face amount | kr										kr 1,500,000,000												kr 1,500,000,000
Net gain on debt extinguishment						$ 4,000,000
Unsecured debt outstanding														$ 182,000,000	165,000,000
Debt instrument, interest rate (as percent)														6.18%			6.18%	6.18%
Percent of principal amount of debt owned						5.50%																	5.50%
Extinguishment of debt, amount | kr							kr 82,000,000
Senior Unsecured Bond | NOK1,500 million bond (NADL) | Norwegian Interbank Offered Rate (NIBOR)
Debt Instrument [Line Items]
Description of variable rate basis										NIBOR
Basis spread on variable rate (as percent)										4.40%
Senior Notes
Debt Instrument [Line Items]
Net gain on debt extinguishment															47,000,000	$ 8,000,000
Senior Notes | $ 600 million bond (NADL)
Debt Instrument [Line Items]
Debt outstanding													$ 165,000,000	$ 187,000,000
Net gain on debt extinguishment						$ 16,000,000
Debt repurchased | kr																							kr 46,900,000
Unsecured debt outstanding														$ 413,000,000	413,000,000
Percent of principal amount of debt owned														31.10%			31.10%	31.10%
Percent of principal amount of debt purchased (as percent)													27.50%
Repayment of long-term debt								$ 25,000,000
Senior Notes | $ 600 million bond (NADL) | North Atlantic Drilling
Debt Instrument [Line Items]
Debt, face amount																								$ 600,000,000
Debt instrument, interest rate (as percent)																								6.25%
Percent of principal amount of debt owned						31.10%																	31.10%
Senior Notes | SEK 1,500 million bond
Debt Instrument [Line Items]
Debt, face amount | kr									kr 1,500,000,000
Unsecured debt outstanding														$ 186,000,000	$ 165,000,000
Senior Notes | SEK 1,500 million bond | STIBOR
Debt Instrument [Line Items]
Description of variable rate basis									STIBOR
Basis spread on variable rate (as percent)									3.25%
Debt instrument, interest rate (as percent)														5.20%			5.20%	5.20%
[1]	In May 2016, we entered into a privately negotiated exchange agreement with certain holders of our outstanding 5.625%(subsequently increased to 6.125%) Senior Notes due in 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 8,184,340 new shares of our common stock, par value $2.00 per share, in exchange for $55 million principal amount of the 2017 Notes. Settlement occurred on May 20, 2016, upon which we had a total of 500,944,280 shares of our common stock issued and outstanding. In June 2016, we entered into another privately negotiated exchange agreement with certain holders of our outstanding 5.625% (subsequently increased to 6.125%) Senior Notes due 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 7,500,000 new shares of our common stock, par value $2.00 per share, in exchange for $50 million principal amount of the 2017 Notes. We had a total of 508,444,280 shares of our common stock issued and outstanding, post settlement on June 13, 2016.

Long-term debt - Covenants cont

Long-term debt - Covenants contained in our debt facilities (Details)

Jan. 01, 2017

Oct. 01, 2016

Apr. 28, 2016credit_facility

Jul. 01, 2015

May 31, 2015

Apr. 30, 2011

Jun. 30, 2017USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2017NOK (kr)

Apr. 04, 2017USD ($)

Feb. 28, 2015USD ($)

Feb. 28, 2015NOK (kr)

May 31, 2014USD ($)

Jan. 31, 2014USD ($)

Oct. 31, 2013NOK (kr)

Sep. 30, 2013USD ($)

Sep. 30, 2012USD ($)

Debt Instrument [Line Items]

Debt covenant, net debt to EBITDA

6

Debt service coverage ratio

1.15

Debt outstanding

$ 8,701,000,000

$ 9,608,000,000

Ship Finance Variable Interest Entities

Debt Instrument [Line Items]

Debt covenant, cash and cash equivalents

$ 25,000,000

Debt covenant, total liabilities to total assets

0.8

0.8

Secured Debt

Debt Instrument [Line Items]

Number of credit facilities maturing in near term | credit_facility

3

$2,000 million facility (NADL) | Secured Debt

Debt Instrument [Line Items]

Debt, face amount

$ 2,000,000,000

Unsecured bonds | $1,000 million bond

Debt Instrument [Line Items]

Debt, face amount

$ 1,000,000,000

$ 1,000,000,000

Debt outstanding

843,000,000

843,000,000

Unsecured bonds | $500 million bond

Debt Instrument [Line Items]

Debt, face amount

500,000,000

Debt outstanding

479,000,000

479,000,000

Unsecured bonds | $ 600 million bond (NADL)

Debt Instrument [Line Items]

Debt, face amount

600,000,000

Debt outstanding

413,000,000

413,000,000

Unsecured bonds | NOK1,500 million bond (NADL)

Debt Instrument [Line Items]

Debt, face amount | kr

kr 1,500,000,000

Debt outstanding

$ 182,000,000

165,000,000

Bank Loans

Debt Instrument [Line Items]

Debt covenant, cash and cash equivalents

$ 250,000,000

$ 150,000,000

Debt covenant, EBITDA to interest expense ratio

2.5

Debt covenant, current assets to current liabilities ratio

1

Debt covenant, percentage of shares in listed companies owned (as percent)

20.00%

Equity ratio (as percent)

30.00%

30.00%

Debt covenant, net debt to EBITDA

4.5

Secured Debt

Debt Instrument [Line Items]

Debt covenant, net debt to EBITDA

6.5

Permitted leverage ratio for period one

6

Permitted leverage ratio for period two

5.5

Permitted leverage ratio for period three

4.5

Debt outstanding

$ 5,581,000,000

$ 6,450,000,000

Secured Debt | Scenario One, Leverage Ratio 4.50 to 4.99 | LIBOR

Debt Instrument [Line Items]

Additional margin payable (as percent)

0.125%

Secured Debt | Scenario One, Leverage Ratio 5.00 to 5.49 | LIBOR

Debt Instrument [Line Items]

Additional margin payable (as percent)

0.25%

Secured Debt | Scenario One, Leverage Ratio 5.50 to 6.00 | LIBOR

Debt Instrument [Line Items]

Additional margin payable (as percent)

0.75%

Secured Debt | Minimum | Scenario One, Leverage Ratio 4.50 to 4.99

Debt Instrument [Line Items]

Leverage ratio

4.5

4.50

Secured Debt | Minimum | Scenario One, Leverage Ratio 5.00 to 5.49

Debt Instrument [Line Items]

Leverage ratio

5

Secured Debt | Minimum | Scenario One, Leverage Ratio 5.50 to 6.00

Debt Instrument [Line Items]

Leverage ratio

5.5

5.50

Secured Debt | Maximum | Scenario One, Leverage Ratio 4.50 to 4.99

Debt Instrument [Line Items]

Leverage ratio

4.99

Secured Debt | Maximum | Scenario One, Leverage Ratio 5.00 to 5.49

Debt Instrument [Line Items]

Leverage ratio

5.49

Secured Debt | Maximum | Scenario One, Leverage Ratio 5.50 to 6.00

Debt Instrument [Line Items]

Debt covenant, net debt to EBITDA

6

Leverage ratio

6

Secured Debt | $2,000 million facility (NADL)

Debt Instrument [Line Items]

Debt, face amount

2,000,000,000

Debt outstanding

897,000,000

$ 1,033,000,000

Debt covenant, collateral to outstanding loan value percentage (as percent)

135.00%

Secured Debt | Credit facility, Ship Finance International Loans, $420 facility | Seadrill Partners LLC

Debt Instrument [Line Items]

Debt, face amount

$ 420,000,000

Senior undersecured or impaired external debt

Debt Instrument [Line Items]

Equity ratio (as percent)

30.00%

Senior Notes | $ 600 million bond (NADL)

Debt Instrument [Line Items]

Debt outstanding

$ 187,000,000

$ 165,000,000

Senior Notes | $ 600 million bond (NADL) | North Atlantic Drilling

Debt Instrument [Line Items]

Debt, face amount

$ 600,000,000

Senior Unsecured Bond | $500 million bond

Debt Instrument [Line Items]

Debt, face amount

$ 500,000,000

Senior Unsecured Bond | NOK1,500 million bond (NADL)

Debt Instrument [Line Items]

Debt, face amount | kr

kr 1,500,000,000

kr 1,500,000,000

Credit facility, International Loans

Debt Instrument [Line Items]

Debt, face amount

$ 475,000,000

Other current liabilities (Deta

Other current liabilities (Details) - USD ($) $ in Millions		Apr. 27, 2017	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Taxes payable			$ 70	$ 148
Deferred mobilization revenue			37	107
Intangible liabilities - unfavorable contracts	[1]		23	43
Employee withheld taxes, social security and vacation payments			15	55
Accrued interest expense			3	69
Construction obligation	[2]		0	500
Derivative financial instruments	[3]		0	236
Accrued expenses			103	116
Other current liabilities			17	78
Total other current liabilities	[4]		$ 268	$ 1,352
Increase in construction obligation		$ 526
[1]	Intangible liabilities represent the estimated fair values of acquired unfavorable drilling contracts. Refer to Note 20 "Goodwill and other intangible assets and liabilities" for more information.
[2]	A construction obligation was recognized upon the acquisition of Sevan Drilling for the Sevan Developer. On April 27, 2017 the construction obligation increased to $526 million following refunds received from Cosco, taking the delivery installment back to the contract price. In July 2017, Sevan and Cosco agreed to further defer the Sevan Developer delivery until June 30, 2020. The contract amendment included a contract termination clause for Cosco and, as Sevan does not have termination rights, it was deemed to have lost control of the asset and therefore derecognized both the newbuild asset, construction obligation and accrued interest. Refer to Note 6 "(Loss)/gain on disposals" for more information.
[3]	On filing for Chapter 11, an event of default under each of our derivative agreements was triggered, resulting in the termination of the derivative financial instruments on September 13, 2017. As a result, the outstanding derivative balance was held at the counterparty claimed value within "Liabilities subject to compromise" on the Consolidated Balance Sheet as at December 31, 2017. Refer to Note 31 "Risk management and financial instruments" for more information.
[4]	Balances held as at December 31, 2017 exclude liabilities that are subject to compromise, which have been reclassified to a separate line within the Consolidated Balance Sheet. This represents our estimate of known or potential pre-petition claims to be resolved in connection with the Chapter 11 proceedings. Refer to Note 1 "General Information".

Other non-current liabilitie143

Other non-current liabilities (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Accrued pension liabilities		$ 6	$ 3
Deferred mobilization revenues		18	55
Intangible liabilities - unfavorable contracts	[1]	0	23
Other non-current liabilities		43	38
Total other non-current liabilities (2)		$ 67	$ 119
[1]	Intangible liabilities represent the estimated fair values of acquired unfavorable drilling contracts. Refer to Note 20 - "Goodwill and other intangible assets and liabilities" for more information.

Common shares (Details)

Common shares (Details) $ / shares in Units, $ in Millions	Sep. 05, 2016$ / sharesshares	Sep. 05, 2016kr / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)shares	Dec. 31, 2017USD ($)$ / sharesshares	Sep. 12, 2017shares	Jun. 30, 2016$ / shares	Jun. 13, 2016shares	May 31, 2016$ / shares	May 20, 2016shares	Nov. 30, 2014	May 10, 2005$ / sharesshares
Class of Stock [Line Items]
Authorized share capital (in shares)			800,000,000	800,000,000	800,000,000
Authorized share capital | $			$ 1,600	$ 1,600	$ 1,600
Common stock, shares issued (in shares)			508,763,020	493,078,680	508,763,020			508,444,280		500,944,280		6,000
Issued and fully paid share capital | $			$ 1,017	$ 986	$ 1,017
Treasury shares held by Company (in shares)			(4,318,740)	(318,740)	(4,244,080)
Treasury shares held by the Company | $			$ (9)	$ (1)	$ (9)
Outstanding shares in issue (in shares)			504,444,280	492,759,940	504,518,940	508,763,020		508,444,280		500,944,280
Outstanding shares in issue | $			$ 1,008	$ 985	$ 1,008
Common shares, par value (in dollars per share) | $ / shares			$ 2		$ 2		$ 2		$ 2			$ 2
Number of shares issued (in shares)			15,684,340
Percent of outstanding shares authorized to be repurchased (as shares)											10.00%
Repurchased shares (in shares)	(4,000,000)	(4,000,000)
Option agreement, strike price (in NOK per share) | $ / shares	$ 20.30
TRS agreements
Class of Stock [Line Items]
Option agreement, strike price (in NOK per share) | kr / shares		kr 20.30
Convertible bonds due 2017
Class of Stock [Line Items]
Number of shares issued due to conversion of convertible debt instruments (in shares)				0

Non-controlling interest - Narr

Non-controlling interest - Narrative (Details) $ / shares in Units, $ in Millions

Dec. 05, 2016USD ($)

Dec. 31, 2015

Jun. 30, 2015USD ($)

Dec. 30, 2014USD ($)

Jan. 02, 2014USD ($)

Oct. 24, 2012USD ($)$ / sharesshares

Dec. 31, 2015

Dec. 31, 2014USD ($)

Jan. 31, 2014USD ($)$ / sharesshares

Dec. 31, 2013shares

Oct. 31, 2013shares

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Dec. 31, 2013USD ($)

Dec. 31, 2012USD ($)company

Mar. 26, 2013

Mar. 25, 2013USD ($)

Noncontrolling Interest [Line Items]

Dividend declared to non controlling interest in VIE

$ 0

Total acquisition price

$ 4

Sale of NCI

(4)

Notional amount of investments acquired

[1]

$ 6

Seadrill Partners LLC

Noncontrolling Interest [Line Items]

Sale of NCI

$ (115)

Notional amount of investments acquired

$ 6.6

Seadrill Mobile Units (Nigeria) Ltd

Noncontrolling Interest [Line Items]

Ownership interest (as percent)

51.00%

Non-controlling interest

Noncontrolling Interest [Line Items]

Dividend declared to non controlling interest in VIE

0

$ 223

Sale of NCI

$ (4)

Asia Offshore Drilling Ltd

Noncontrolling Interest [Line Items]

Noncontrolling interest ownership percentage (as percent)

66.18%

Fair value of establishment of non-controlling interest

$ 100

SFL West Polaris Limited

Noncontrolling Interest [Line Items]

Total acquisition price

$ 111

Deemed contribution to Seadrill shareholders from non-controlling interest

$ 7

North Atlantic Drilling

Noncontrolling Interest [Line Items]

Noncontrolling interest ownership percentage (as percent)

70.36%

Reverse stock split conversion ratio

0.1

0.1

North Atlantic Drilling | IPO

Noncontrolling Interest [Line Items]

New shares issued by equity method investment (in shares) | shares

13,513,514

Sale of stock (in dollars per share) | $ / shares

$ 9.25

Noncontrolling interest, increase from subsidiary equity issuance

$ 52

Asia Offshore Drilling Ltd

Noncontrolling Interest [Line Items]

Noncontrolling interest ownership percentage (as percent)

66.24%

66.21%

Sevan Drilling ASA

Noncontrolling Interest [Line Items]

Noncontrolling interest ownership percentage (as percent)

50.11%

Ship Finance International Ltd VIEs

Noncontrolling Interest [Line Items]

Number of Ship Finance companies acquired | company

1

Acquisition of remaining equity shares of former VIE

$ 47

Proceeds from dividends received

$ 14

$ 113

Seadrill Partners LLC

Noncontrolling Interest [Line Items]

Noncontrolling interest ownership percentage (as percent)

75.67%

77.47%

62.35%

Common units representing liability entity's interests (in shares) | shares

10,062,500

Common unit price representing liability entity's interests (in USD per share) | $ / shares

$ 22

Gross proceeds from completion of IPO

$ 221

Consideration received from shares issued

$ 203

Common units issued in connection with an over allotment option (in shares) | shares

1,312,500

Common units owned upon completion of IPO (in shares) | shares

14,752,525

Subordinated units owned upon completion of IPO (in shares) | shares

16,543,350

Seadrill Partners LLC | Stock Issued to Reporting Entity

Noncontrolling Interest [Line Items]

New shares issued by equity method investment (in shares) | shares

3,394,916

3,310,622

Seadrill Partners LLC | Stock Issued to Public

Noncontrolling Interest [Line Items]

New shares issued by equity method investment (in shares) | shares

12,880,000

Noncontrolling interest, increase from subsidiary equity issuance

$ 239

Seadrill UK Ltd | Seadrill Mobile Units (Nigeria) Ltd

Noncontrolling Interest [Line Items]

Ownership interest (as percent)

49.00%

Interest acquired (as percent)

10.00%

Notional amount of investments acquired

$ 6.6

HHL | Seadrill Mobile Units (Nigeria) Ltd

Noncontrolling Interest [Line Items]

Notional amount of investments acquired

$ 6.6

Business acquisition, percentage of voting interests acquired

2.00%

Investments, consideration paid

$ 0.3

[1]

uring the year ended December 31, 2016, certain consolidated VIEs of ours withdrew bank loans and made loans to the related party Ship Finance International. These balances are presented net in the consolidated statement of cash flows. Refer to Note 22 "Long-term debt" for further information.

Non-controlling interest - Chan

Non-controlling interest - Changes in Non-controlling Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in non-controlling interest [Roll Forward]
Balance, beginning of period	$ 542	$ 615	$ 626
Changes during period	(14)	(99)	(10)
Net income attributable to non-controlling interest	(129)	26	(1)
Impairment of goodwill			(94)
Balance, end of period	399	542	615
As previously filed on Form 20-F
Changes in non-controlling interest [Roll Forward]
Net income attributable to non-controlling interest		26	93
Ship Finance International Ltd VIEs
Changes in non-controlling interest [Roll Forward]
Balance, beginning of period	(69)	14	32
Changes during period	(14)	(112)	0
Net income attributable to non-controlling interest	24
Impairment of goodwill			(48)
Balance, end of period	(59)	(69)	14
Ship Finance International Ltd VIEs | As previously filed on Form 20-F
Changes in non-controlling interest [Roll Forward]
Net income attributable to non-controlling interest		29	30
North Atlantic Drilling Ltd
Changes in non-controlling interest [Roll Forward]
Balance, beginning of period	165	179	205
Changes during period	0	7	8
Net income attributable to non-controlling interest	(89)
Impairment of goodwill			(18)
Balance, end of period	76	165	179
North Atlantic Drilling Ltd | As previously filed on Form 20-F
Changes in non-controlling interest [Roll Forward]
Net income attributable to non-controlling interest		(21)	(16)
Asia Offshore Drilling Ltd
Changes in non-controlling interest [Roll Forward]
Balance, beginning of period	149	140	134
Changes during period	0	0	(14)
Net income attributable to non-controlling interest	0
Impairment of goodwill			0
Balance, end of period	149	149	140
Asia Offshore Drilling Ltd | As previously filed on Form 20-F
Changes in non-controlling interest [Roll Forward]
Net income attributable to non-controlling interest		9	20
Sevan Drilling ASA
Changes in non-controlling interest [Roll Forward]
Balance, beginning of period	291	282	251
Changes during period	0	0	0
Net income attributable to non-controlling interest	(65)
Impairment of goodwill			(28)
Balance, end of period	226	291	282
Sevan Drilling ASA | As previously filed on Form 20-F
Changes in non-controlling interest [Roll Forward]
Net income attributable to non-controlling interest		9	59
Seadrill Nigeria Operations Limited
Changes in non-controlling interest [Roll Forward]
Balance, beginning of period	6	0	4
Changes during period	0	6	(4)
Net income attributable to non-controlling interest	1
Impairment of goodwill			0
Balance, end of period	$ 7	6	0
Seadrill Nigeria Operations Limited | As previously filed on Form 20-F
Changes in non-controlling interest [Roll Forward]
Net income attributable to non-controlling interest		$ 0	$ 0

Accumulated other comprehens147

Accumulated other comprehensive income/(loss) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 10,063,000,000	$ 10,068,000,000
Other comprehensive income before reclassifications	15,000,000
Amounts reclassified from accumulated other comprehensive income	(10,000,000)
Ending balance	6,959,000,000	10,063,000,000
Other comprehensive income taxes	0
Actuarial loss related to pension, tax effect	$ 1,000,000	$ 1,000,000
Tax rate in Norway (as percent)	24.00%	24.00%
Unrealized gain on marketable securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 17,000,000
Other comprehensive income before reclassifications	14,000,000
Amounts reclassified from accumulated other comprehensive income	0
Ending balance	31,000,000	$ 17,000,000
Unrealized gain on foreign exchange
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	36,000,000
Other comprehensive income before reclassifications	0
Amounts reclassified from accumulated other comprehensive income	0
Ending balance	36,000,000	36,000,000
Actuarial gain/(loss) relating to pension
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(23,000,000)
Other comprehensive income before reclassifications	(3,000,000)
Amounts reclassified from accumulated other comprehensive income	0
Ending balance	(26,000,000)	(23,000,000)
Share in unrealized gains from associated companies
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	23,000,000
Other comprehensive income before reclassifications	2,000,000
Amounts reclassified from accumulated other comprehensive income	(10,000,000)
Ending balance	15,000,000	23,000,000
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0
Other comprehensive income before reclassifications	2,000,000
Amounts reclassified from accumulated other comprehensive income	0
Ending balance	2,000,000	0
Accumulated other comprehensive income/(loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	53,000,000	(142,000,000)
Ending balance	$ 58,000,000	$ 53,000,000

Share based compensation (Detai

Share based compensation (Details)

1 Months Ended

12 Months Ended

Dec. 31, 2015$ / sharesshares

Oct. 31, 2013$ / shares

Oct. 31, 2013kr / shares

Nov. 30, 2011$ / shares

Nov. 30, 2011kr / shares

Nov. 30, 2010$ / shares

Nov. 30, 2010kr / shares

Dec. 31, 2017USD ($)shares

Dec. 31, 2016USD ($)shares

Dec. 31, 2015USD ($)$ / sharesshares

Dec. 31, 2012$ / shares

Dec. 31, 2012kr / shares

Dec. 31, 2014shares

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Share options granted recognized as personnel expenses | $

$ 7,000,000

$ 7,000,000

$ 7,000,000

Vesting period

12 months

12 months

Tranche One

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

13 months

13 months

18 months

18 months

Tranche Two

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

25 months

25 months

36 months

36 months

Tranche Three

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

37 months

37 months

48 months

48 months

Tranche Four

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

49 months

49 months

60 months

60 months

Restricted Stock Units (RSUs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Unrecognized compensation costs | $

$ 9,000,000

Period for recognizing unrecognized costs

1 year

Vesting period

3 years

Stock Options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Options granted to Americans, exercise price (in currency per share) | (per share)

$ 31.40

kr 192.90

Options granted to non-Americans, exercise price (in currency per share) | (per share)

$ 31.06

kr 185.20

Options, exercise price (in currency per share) | (per share)

$ 93.70

$ 34.68

kr 202.10

Weighted average grant-date fair value of options granted (in USD per share) | $ / shares

$ 10.23

$ 3.33

$ 10.23

Risk-free interest rate (as percent)

1.60%

Volatility (as percent)

34.80%

Dividend yield (as percent)

0.00%

Vesting of options granted (as percent)

100.00%

Options, weighted average remaining contractual life

9 months

34 months

Total intrinsic value of options exercised | $

$ 0

$ 0

$ 0

Intrinsic value of options fully vested but not exercised | $

$ 0

Stock Options | Tranche One

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting rights percentage

33.33%

25.00%

25.00%

25.00%

25.00%

20.00%

20.00%

Stock Options | Tranche Two

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting rights percentage

33.33%

25.00%

25.00%

25.00%

25.00%

Stock Options | Tranche Three

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting rights percentage

33.33%

25.00%

25.00%

25.00%

25.00%

Stock Options | Tranche Four

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting rights percentage

33.33%

25.00%

25.00%

25.00%

25.00%

Stock Options | Seadrill Scheme

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Options outstanding (in shares) | shares

2,015,171

537,500

947,500

2,015,171

2,241,116

Stock Options | Minimum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Options, exercise price (in currency per share) | kr / shares

kr 249

Options, exercise price range, lower range limit (in currency per share) | kr / shares

kr 205.30

Stock Options | Minimum | Seadrill Scheme

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

1 year

Stock Options | Maximum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Options, exercise price (in currency per share) | kr / shares

kr 273

Options, exercise price range, upper range limit (in currency per share) | kr / shares

kr 224.53

Stock Options | Maximum | Seadrill Scheme

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

5 years

Share based compensation - Opti

Share based compensation - Options Outstanding (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Granted (in shares)	0
Seadrill Scheme
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of year (in shares)	947,500	2,015,171	2,241,116
Granted (in shares)		0	710,000
Exercised (in shares)	0	0	0
Forfeited (in shares)	(410,000)	(1,067,671)	(935,945)
Outstanding at end of year (in shares)	537,500	947,500	2,015,171
Exercisable at end of year (in shares)	358,959	412,917	882,152
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding at beginning of year (in US dollars per share)	$ 20.08	$ 28.53	$ 35.10
Granted (in US dollars per share)	0	0	12.04
Exercised (in US dollars per share)	0	0	0
Forfeited (in US dollars per share)	22.06	35.29	32.81
Outstanding at end of year (in US dollars per share)	11.62	20.08	28.53
Exercisable at end of year (in US dollars per share)	$ 11.65	$ 25.79	$ 36.14

Share based compensation - Rest

Share based compensation - Restricted Stock Units Narrative (Details)		Dec. 31, 2015$ / sharesshares	Nov. 07, 2013$ / sharesshares	Oct. 01, 2013$ / sharesshares	Dec. 31, 2016$ / sharesshares	Apr. 30, 2016$ / sharesshares	Dec. 31, 2015$ / sharesshares	May 31, 2015$ / sharesshares	Jan. 31, 2015$ / sharesshares	Dec. 31, 2014$ / sharesshares	Nov. 30, 2010	Dec. 31, 2017$ / sharesshares	Dec. 31, 2016$ / sharesshares	Dec. 31, 2015$ / sharesshares	Jun. 30, 2016$ / shares	May 31, 2016$ / shares	Dec. 30, 2015$ / shares	May 10, 2005$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period											12 months
Common shares, par value (in dollars per share) | $ / shares					$ 2							$ 2	$ 2		$ 2	$ 2		$ 2
North Atlantic Drilling
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reverse stock split conversion ratio		0.1					0.1
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period												3 years
Number of shares authorized (in shares)		909,970		373,700			909,970			162,560				909,970
Weighted average grant date fair value (in currency per share) | $ / shares				$ 46.07	$ 3.81	$ 3.82	$ 3.67	$ 11.91		$ 11
Shares granted (in shares)					2,282,500	2,066,658		28,000				0	4,349,158	937,970
Restricted Stock Units (RSUs) | North Atlantic Drilling
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)		1,478,500	278,778				1,478,500							1,478,500
Weighted average grant date fair value (in currency per share) | $ / shares			$ 96.50		$ 3.62	$ 2.95	$ 3.70		$ 14.10
Shares granted (in shares)					152,000	118,653			109,219			0	270,653	1,587,719
Common shares, par value (in dollars per share) | $ / shares		$ 0.10					$ 0.10							$ 0.10			$ 5
Adjustment (in shares)	[1]						1,571,250					0	0	1,571,251
[1]	Adjustment relates to NADL's reverse stock split in December 2015, as discussed above.

Share based compensation - R151

Share based compensation - Restricted Stock Unit Activity (Details) - Restricted Stock Units (RSUs) - shares		1 Months Ended					12 Months Ended
		Dec. 31, 2016	Apr. 30, 2016	Dec. 31, 2015	May 31, 2015	Jan. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding at beginning of year (in shares)						525,210	5,186,724	1,402,980	525,210
Granted (in shares)		2,282,500	2,066,658		28,000		0	4,349,158	937,970
Settled (in shares)							(74,660)	(249,050)	0
Forfeited (in shares)							(798,127)	(316,364)	(60,200)
Outstanding at end of year (in shares)		5,186,724		1,402,980			4,313,937	5,186,724	1,402,980
North Atlantic Drilling
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding at beginning of year (in shares)						253,870	413,702	174,583	253,870
Granted (in shares)		152,000	118,653			109,219	0	270,653	1,587,719
Settled (in shares)							0	(20,837)	0
Adjustment (in shares)	[1]			(1,571,250)			0	0	(1,571,251)
Forfeited (in shares)							(300)	(10,697)	(95,755)
Outstanding at end of year (in shares)		413,702		174,583			413,402	413,702	174,583
[1]	Adjustment relates to NADL's reverse stock split in December 2015, as discussed above.

Pension benefits - Narrative (D

Pension benefits - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Defined Benefit Plan Disclosure [Line Items]
Impact of settlement/curtailment funded status	$ 1	$ 1	$ 0
Accumulated benefit obligation	33	54
Total company contributions	$ 17	$ 26	$ 29
Onshore Employees
Defined Benefit Plan Disclosure [Line Items]
Retirement pension as a percent of salary (as percent)	66.00%
Retirement age	67 years
Retirement pension cap (as percent)	66.00%
Multiple of base	12
Retirement age to receive pre-retirement pension	62 years
Offshore Employees
Defined Benefit Plan Disclosure [Line Items]
Retirement pension as a percent of salary (as percent)	60.00%
Retirement age	67 years
Offshore Employees, Mobile Units
Defined Benefit Plan Disclosure [Line Items]
Retirement age to receive pre-retirement pension	60 years

Pension benefits - Consolidated

Pension benefits - Consolidated Balance Sheet Position (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Accrued pension liabilities - Non-current liabilities	$ 6	$ 3
Less: Deferred tax (Asset)	(2)	(1)
Shareholders equity	$ 4	$ 2

Pension benefits - Annual Pensi

Pension benefits - Annual Pension Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Service cost	$ 2	$ 7	$ 12
Interest cost	2	3	4
Gross pension cost for the year	4	10	16
Expected return on plan assets	(1)	(4)	(3)
Administration charges	0	0	1
Net pension cost for the year	3	6	14
Social security cost	0	1	2
Amortization of actuarial gains/losses	0	1	3
Impact of settlement/curtailment funded status	(1)	(1)	0
Total net pension cost	$ 2	$ 7	$ 19

Pension benefits - Funded Statu

Pension benefits - Funded Status of the Defined Benefit Plan (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Projected benefit obligations at end of period	$ 38	$ 60	$ 130
Plan assets at market value	(33)	(58)	$ (97)
Accrued pension liability exclusive social security	5	2
Social security related to pension obligations	1	1
Accrued pension liabilities	$ 6	$ 3

Pension benefits - Change in Pr

Pension benefits - Change in Projected Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligations at beginning of period	$ 60	$ 130
Interest cost	2	3	$ 4
Service cost	2	7	12
Benefits paid	(2)	(3)
Change in unrecognized actuarial gain	(3)	(28)
Settlement	(24)	(54)
Foreign currency translations	3	5
Projected benefit obligations at end of period	$ 38	$ 60	$ 130

Pension benefits - Change in Pe

Pension benefits - Change in Pension Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 58	$ 97
Estimated return	1	4
Contribution by employer	1	9
Administration charges	0	0	$ (1)
Benefits paid	(2)	(3)
Change in unrecognized actuarial loss	(5)	(1)
Settlement	(23)	(52)
Foreign currency translations	3	4
Fair value of plan assets at end of year	$ 33	$ 58	$ 97

Pension benefits - Assumptions

Pension benefits - Assumptions Used in Calculation of Pension Obligations (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Rate of compensation increase at the end of year (as percent)	2.50%	2.50%	2.50%
Discount rate at the end of year (as percent)	2.40%	2.10%	2.70%
Prescribed pension index factor (as percent)	1.50%	1.20%	1.20%
Expected return on plan assets for the year (as percent)	2.40%	3.00%	3.30%
Employee turnover (as percent)	4.00%	4.00%	4.00%
Expected increases in Social Security Base (as percent)	2.25%	2.25%	2.50%

Pension benefits - Weighted-Ave

Pension benefits - Weighted-Average Asset Allocation of Funds Related to Defined Benefit Plan (Details)	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation of funds related to defined benefit plan (as percent)	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation of funds related to defined benefit plan (as percent)	10.60%	7.10%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation of funds related to defined benefit plan (as percent)	66.10%	54.70%
Real estate
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation of funds related to defined benefit plan (as percent)	8.80%	9.40%
Money market
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation of funds related to defined benefit plan (as percent)	13.50%	28.10%
Other
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation of funds related to defined benefit plan (as percent)	1.00%	0.70%

Pension benefits - Expected Ann

Pension benefits - Expected Annual Pension Plan Contributions Under Defined Benefit Plans (Details) $ in Millions	Dec. 31, 2017USD ($)
Retirement Benefits [Abstract]
2,018	$ 3
2,019	3
2,020	3
2,021	3
2,022	3
2023-2027	15
Total payments expected during the next 10 years	$ 30

Related party transactions - Se

Related party transactions - Seadrill Partners Related Party Net Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Intra group revenues		$ 110	$ 100	$ 119
Contingent consideration realized	[1]	27	21	47	[2]
Seadrill Partners LLC | Subsidiaries
Related Party Transaction [Line Items]
Intra group revenues	[3],[4]	75	65	75
Contingent consideration realized		27	21	47
Rig operating expenses recharged by Seadrill Partners	[5]	(5)	(11)	(13)
Bareboat charter arrangements	[6]	3	10	2
Intercompany inventory purchases		(2)	(1)	0
Interest recognized	[7]	6	12	16
Derivatives recharged to Seadrill Partners	[8]	1	4	10
Net related party income from Seadrill Partners		144	146	190
Seadrill Partners LLC | Subsidiaries | Rig Operating Expenses Charged
Related Party Transaction [Line Items]
Other revenues	[9]	23	25	29
Seadrill Partners LLC | Subsidiaries | Insurance Premiums Charged
Related Party Transaction [Line Items]
Other revenues	[10]	11	16	20
Seadrill Partners LLC | Subsidiaries | Deferred Consideration Receivable, Disposals
Related Party Transaction [Line Items]
Interest recognized		$ 5	$ 5	$ 8
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".
[2]	Text selection found with no content.
[3]	Management and administrative service agreementsCertain subsidiaries of Seadrill Partners are in a management and administrative services agreement with Seadrill Management, a wholly owned subsidiary of Seadrill, pursuant to which Seadrill Management provides to Seadrill Partners certain management and administrative services. The services provided by Seadrill Management are charged at cost plus management fee to be agreed upon from time to time by the parties. In April 2016, the agreement was extended for an indefinite term and can be terminated providing 90 days written notice. During the twelve months ended December 31, 2017, the management fee has ranged from 4.85% to 8% of costs and expenses incurred in connection with providing these services.
[4]	Technical and administrative service agreement Certain subsidiaries of Seadrill Partners entered into advisory, technical and/or administrative services agreements with subsidiaries of Seadrill. The services provided by our subsidiaries are charged at cost plus service fee equal to approximately 5% of costs and expenses incurred in connection with providing these services. Income recognized under the above agreements (a) & (b) for the period ended December 31, 2017 was $75 million (2016: $65 million; 2015: $75 million).
[5]	Rig operating costs charged by Seadrill PartnersSeadrill Partners has charged to Seadrill, through its Nigerian service company, certain services, including the provision of onshore and offshore personnel, which was provided for the West Jupiter and West Saturn drilling rigs operating in Nigeria. The total rig operating expenses incurred for the period ending December 31, 2017 was $5 million (2016: $11 million; 2015: $13 million).
[6]	Bareboat charter arrangementsIn connection with the transfer of the West Aquarius operations to Canada, the West Aquarius drilling contract was assigned to Seadrill Canada Ltd., a wholly owned subsidiary of Seadrill Partners, necessitating certain changes to the related party contractual arrangements relating to the West Aquarius. Seadrill China Operations Ltd, the owner of the West Aquarius and a wholly-owned subsidiary of Seadrill Partners, had previously entered into a bareboat charter arrangement with Seadrill Offshore AS, a wholly-owned subsidiary of Seadrill, providing Seadrill Offshore AS with the right to use the West Aquarius. In October 2012, this bareboat charter arrangement was replaced with a new bareboat charter between Seadrill China Operations Ltd and Seadrill Offshore AS, and at the same time, Seadrill Offshore AS entered into a bareboat charter arrangement providing Seadrill Canada Ltd. with the right to use the West Aquarius in order to perform its obligations under the drilling contract described above. For year ended December 31, 2017 the net effect to Seadrill of the bareboat charters was an expense of $3 million (2016: $10 million, 2015: $2 million).The contract was terminated effective April 19, 2017 on completion of the rig's contract with Hibernia Management.
[7]	Interest expenses and loss on derivativesThe total interest charged to Seadrill Partners for the loan arrangements, including commitment fees and other fees, was $6 million for the period ending December 31, 2017 (2016: $12 million; 2015: $16 million). Refer to the sections below for details on the financing arrangements.
[8]	Derivative interest rate swap agreementsWe previously held interest rate swap agreements with Seadrill Partners on a back to back basis with certain of our own interest rate swap agreements. On commencement of Chapter 11 proceedings the derivative position held by Seadrill was cancelled and held at the claimed value by the derivative counterparty. This resulted in no further recharged gains or losses on derivatives after September 12, 2017. The total net derivative gains and losses charged to Seadrill Partners for the year ended December 31, 2017 was $1 million, (2016: $1 million; 2015: $10 million).
[9]	Rig operating costs charged to Seadrill PartnersWe have charged to Seadrill Partners certain rig operating costs in relation to costs incurred on behalf of the West Polaris operating in Angola in 2017, 2016 and 2015 and the West Vencedor which operated in Angola in 2015. The total other revenues earned for the year ending December 31, 2017 was $23 million (2016: $25 million; 2015: $29 million).
[10]	Insurance premiumsWe negotiate insurance for drilling units on a centralized basis. The total insurance premiums related to Seadrill Partners drilling units recharged to Seadrill Partners were $10.5 million for the year ending December 31, 2017 (2016: $16 million; 2015: $20 million).

Related party transactions - Re

Related party transactions - Receivables (payables) with Seadrill Partners (Details) - Seadrill Partners LLC - Equity Method Investee - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	May 31, 2013
Rig Financing Agreements
Related Party Transaction [Line Items]
Receivables (payables)	[1]	$ 25	$ 160
Vendor Financing Loan
Related Party Transaction [Line Items]
Receivables (payables)	[2]	0	0
Loans receivable, related parties				$ 109.5
Deferred Consideration Receivable, Disposals
Related Party Transaction [Line Items]
Receivables (payables)	[3]	52	61
Other Receivables
Related Party Transaction [Line Items]
Receivables (payables)	[4]	157	189
Other Payables
Related Party Transaction [Line Items]
Receivables (payables)	[4]	$ (24)	$ (80)
[1]	Rig Financing Agreements West Vencedor Facility - In June 2014 we repaid the underlying $1,200 million senior secured loan relating to the West Vencedor, and as a result the West Vencedor Loan Agreement between us and Seadrill Partners was amended to carry on the existing loan on the same terms. The West Vencedor Loan Agreement between us and Seadrill Partners was scheduled to mature in June 2015 and all outstanding amounts thereunder would be due and payable, including a balloon payment of $70 million. On April 14, 2015 the Loan Agreement was amended and the maturity date was extended to June 25, 2018. The West Vencedor Loan Agreement bears a margin of 2.25%, a guarantee fee of 1.4% and a balloon payment of $21 million due at maturity in June 2018. The total amount owed by Seadrill Partners to Seadrill under the remaining West Vencedor Loan agreement as at December 31, 2017 was $25 million (December 31, 2016: $41 million).T-15 / T-16 Facility - The total amounts owed under the Rig Financing Agreement relating to the T-15 and T-16 were amended in August 2017 so that the facility is held in Seadrill Partners therefore removing the back to back agreement with Seadrill. As a result, the total amount outstanding at at December 31, 2017 was nil (December 31, 2016: $119 million). West Vela facility - Under the terms of the $1,450 million secured credit facility agreement, certain subsidiaries of Seadrill and Seadrill Partners relating to the West Vela and West Tellus, were jointly and severally liable for their own debt and obligations under the facility and the debt and obligations of other borrowers who are also party to such agreement. In August 2017, Seadrill Partners completed amendments to the facility to insulate itself from events of default related to our potential use of Chapter 11 proceedings to implement our restructuring plan. The amendments remove Seadrill as a guarantor for this facility. West Polaris facility - In June 2015, we completed the sale of the entities that own and operate the West Polaris to Seadrill Partners. One of the entities sold was the sole borrower under $420 million senior secured credit facility. Refer to Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information. Prior to August 2017, we acted as a guarantor under the facility. In August 2017, Seadrill Partners completed amendments to the facility to insulate itself from events of default related to our potential use of Chapter 11 proceedings to implement our restructuring plan. The amendments remove Seadrill as a guarantor for this facility.
[2]	$109.5 million Vendor financing loanIn May 2013, Seadrill Partners borrowed $109.5 million from Seadrill as vendor financing to fund the acquisition of the T-15. The loan bore interest at a rate of LIBOR plus a margin of 5% and matured in May 2016.
[3]	Deferred consideration receivableOn the disposal of the West Vela and West Polaris to Seadrill Partners, we recognized deferred consideration receivables. Refer to the sections below for more information.West Polaris DisposalOn June 19, 2015, we sold the entities that owned and operated the West Polaris (the “Polaris business”), to Seadrill Operating LP (“Seadrill Operating”), a consolidated subsidiary of Seadrill Partners LLC and 42% owned by us. The entities continue to be related parties subsequent to the sale. In August 2017, Seadrill Partners completed amendments to the facility to insulate itself from events of default related to our potential use of Chapter 11 proceedings to implement our restructuring plan. The amendments remove Seadrill as a guarantor for this facility. Refer to Note 11 "Disposals of businesses and deconsolidation of subsidiaries" for more information.
[4]	Receivables and PayablesReceivables and payables with Seadrill Partners and its subsidiaries are comprised of management fees, advisory and administrative services, and other items including accrued interest. In addition, certain receivables and payables arise when we pay an invoice on behalf of Seadrill Partners or its subsidiaries and vice versa. Receivables and payables are generally settled quarterly in arrears. Trading balances to Seadrill Partners and its subsidiaries are unsecured and are intended to be settled in the ordinary course of business.West Sirius bareboat charter financing loanIn December 2015, an operating subsidiary of Seadrill Partners borrowed from a subsidiary of Seadrill $143 million in order to provide sufficient immediate liquidity to meet the terms of its bareboat charter termination payment in connection with the West Sirius contract termination. The loan bears interest at a rate of LIBOR plus 0.56% and matured in July 2017. The loan was repaid in full during the year ended December 31, 2017 (December 31, 2016 outstanding balance: $39 million). Concurrently, Seadrill borrowed $143 million from a rig owning subsidiary of Seadrill Partners in order to restore its liquidity with respect to the West Sirius bareboat charter financing loan referred to above. The loan bears interest at a rate of LIBOR plus 0.56% and matures in July 2017. The loan was repaid in full during the year ended December 31, 2017 (December 31, 2016: $39 million). Each of the loan parties understand and agree that the loan agreements act in parallel with each other. These transactions have been classified within current and non-current portions of "Amount due from related parties", "Amounts due to related parties" and "Long-term debt due to related parties".West Sirius Spare parts agreementDuring the year ended December 31, 2015, a subsidiary of Seadrill entered into an agreement with Seadrill Partners to store spare parts of Seadrill Partners’ West Sirius rig while it is stacked. We are responsible at our own cost for the moving and storing of the spare parts during the stacking period. We may use the spare parts of the West Sirius during the stacking period, but must replace them as required by Seadrill Partners at its own cost. GuaranteesSeadrill provides certain guarantees on behalf of Seadrill Partners.•Guarantees in favor of customers, which guarantee the performance of the Seadrill Partners drilling units, totaled $165 million as at December 31, 2017 (2016: $185 million); •Guarantees in favor of banks provided on behalf of Seadrill Partners totaled nil as at December 31, 2017 after Seadrill Partners insulated itself from us in August 2017 (2016: $621 million); and •Guarantees in favor of suppliers provided on behalf of Seadrill Partners, relating to custom guarantees in Nigeria, totaled $0.6 million (2016: $0.4 million).

Related party transactions -163

Related party transactions - Related Party Agreements with Seadrill Partners Narrative (Details) - USD ($)		Apr. 14, 2015	Apr. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Jun. 30, 2014	Jan. 02, 2014
Related Party Transaction [Line Items]
Revenues related party				$ 110,000,000	$ 100,000,000	$ 119,000,000
Secured Debt | US$1,200 facility
Related Party Transaction [Line Items]
Maximum borrowing capacity								$ 1,200,000,000
Seadrill Partners LLC | Secured Debt | West Vencedor Loan Agreement
Related Party Transaction [Line Items]
Balloon payment to be paid		$ 21,000,000					$ 70,000,000
Basis spread on variable rate (as percent)		2.25%
Guarantee fee percentage (as percent)		1.40%
Equity Method Investee | Minimum
Related Party Transaction [Line Items]
Management fee (as percent)				4.50%
Equity Method Investee | Maximum
Related Party Transaction [Line Items]
Management fee (as percent)				8.00%
Equity Method Investee | Seadrill Partners LLC
Related Party Transaction [Line Items]
Technical and administrative service agreement fee (as percent)									5.00%
Equity Method Investee | Seadrill Partners LLC | Seadrill Management
Related Party Transaction [Line Items]
Management service agreement termination notice period			90 days
Equity Method Investee | Seadrill Partners LLC | Seadrill Management | Minimum
Related Party Transaction [Line Items]
Management fee (as percent)				4.85%
Equity Method Investee | Seadrill Partners LLC | Seadrill Management | Maximum
Related Party Transaction [Line Items]
Management fee (as percent)				8.00%
Subsidiaries | Rig Financing Agreements
Related Party Transaction [Line Items]
Interest income, related party				$ 6,000,000	12,000,000	16,000,000
Subsidiaries | Seadrill Partners LLC
Related Party Transaction [Line Items]
Revenues related party	[1],[2]			75,000,000	65,000,000	75,000,000
Rig operating expenses recharged by Seadrill Partners	[3]			5,000,000	11,000,000	13,000,000
Bareboat charter arrangements	[4]			3,000,000	10,000,000	2,000,000
Interest income, related party	[5]			6,000,000	12,000,000	16,000,000
Derivatives recharged to Seadrill Partners	[6]			1,000,000	4,000,000	10,000,000
Subsidiaries | Seadrill Partners LLC | Interest Rate Swap
Related Party Transaction [Line Items]
Derivatives recharged to Seadrill Partners				1,000,000	1,000,000	$ 10,000,000
Affiliated Entity | Rig Financing Agreements
Related Party Transaction [Line Items]
Due from related parties				0	119,000,000
Affiliated Entity | West Vencedor | Rig Financing Agreements
Related Party Transaction [Line Items]
Due from related parties				$ 25,000,000	$ 41,000,000
[1]	Management and administrative service agreementsCertain subsidiaries of Seadrill Partners are in a management and administrative services agreement with Seadrill Management, a wholly owned subsidiary of Seadrill, pursuant to which Seadrill Management provides to Seadrill Partners certain management and administrative services. The services provided by Seadrill Management are charged at cost plus management fee to be agreed upon from time to time by the parties. In April 2016, the agreement was extended for an indefinite term and can be terminated providing 90 days written notice. During the twelve months ended December 31, 2017, the management fee has ranged from 4.85% to 8% of costs and expenses incurred in connection with providing these services.
[2]	Technical and administrative service agreement Certain subsidiaries of Seadrill Partners entered into advisory, technical and/or administrative services agreements with subsidiaries of Seadrill. The services provided by our subsidiaries are charged at cost plus service fee equal to approximately 5% of costs and expenses incurred in connection with providing these services. Income recognized under the above agreements (a) & (b) for the period ended December 31, 2017 was $75 million (2016: $65 million; 2015: $75 million).
[3]	Rig operating costs charged by Seadrill PartnersSeadrill Partners has charged to Seadrill, through its Nigerian service company, certain services, including the provision of onshore and offshore personnel, which was provided for the West Jupiter and West Saturn drilling rigs operating in Nigeria. The total rig operating expenses incurred for the period ending December 31, 2017 was $5 million (2016: $11 million; 2015: $13 million).
[4]	Bareboat charter arrangementsIn connection with the transfer of the West Aquarius operations to Canada, the West Aquarius drilling contract was assigned to Seadrill Canada Ltd., a wholly owned subsidiary of Seadrill Partners, necessitating certain changes to the related party contractual arrangements relating to the West Aquarius. Seadrill China Operations Ltd, the owner of the West Aquarius and a wholly-owned subsidiary of Seadrill Partners, had previously entered into a bareboat charter arrangement with Seadrill Offshore AS, a wholly-owned subsidiary of Seadrill, providing Seadrill Offshore AS with the right to use the West Aquarius. In October 2012, this bareboat charter arrangement was replaced with a new bareboat charter between Seadrill China Operations Ltd and Seadrill Offshore AS, and at the same time, Seadrill Offshore AS entered into a bareboat charter arrangement providing Seadrill Canada Ltd. with the right to use the West Aquarius in order to perform its obligations under the drilling contract described above. For year ended December 31, 2017 the net effect to Seadrill of the bareboat charters was an expense of $3 million (2016: $10 million, 2015: $2 million).The contract was terminated effective April 19, 2017 on completion of the rig's contract with Hibernia Management.
[5]	Interest expenses and loss on derivativesThe total interest charged to Seadrill Partners for the loan arrangements, including commitment fees and other fees, was $6 million for the period ending December 31, 2017 (2016: $12 million; 2015: $16 million). Refer to the sections below for details on the financing arrangements.
[6]	Derivative interest rate swap agreementsWe previously held interest rate swap agreements with Seadrill Partners on a back to back basis with certain of our own interest rate swap agreements. On commencement of Chapter 11 proceedings the derivative position held by Seadrill was cancelled and held at the claimed value by the derivative counterparty. This resulted in no further recharged gains or losses on derivatives after September 12, 2017. The total net derivative gains and losses charged to Seadrill Partners for the year ended December 31, 2017 was $1 million, (2016: $1 million; 2015: $10 million).

Related party transactions - Ri

Related party transactions - Rig Financing Agreements (Details) - USD ($)	Apr. 14, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	[1]	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2013
Related Party Transaction [Line Items]
Payments received from loans granted to related parties		$ 66,000,000	$ 283,000,000	$ 233,000,000
Secured Debt | $1,450 million facility
Related Party Transaction [Line Items]
Debt, face amount		1,450,000,000						$ 1,450,000,000
Ship Finance International Loans, $700 facility | SFL West Polaris Limited
Related Party Transaction [Line Items]
Debt, face amount						$ 420,000,000
Secured Debt | US$1,200 facility
Related Party Transaction [Line Items]
Maximum borrowing capacity							$ 1,200,000,000
Affiliated Entity | Rig Financing Agreements
Related Party Transaction [Line Items]
Due from related parties		0	119,000,000
Affiliated Entity | West Vencedor | Rig Financing Agreements
Related Party Transaction [Line Items]
Due from related parties		$ 25,000,000	$ 41,000,000
Seadrill Partners LLC | Secured Debt | West Vencedor Loan Agreement
Related Party Transaction [Line Items]
Balloon payment to be paid	$ 21,000,000					$ 70,000,000
Basis spread on variable rate (as percent)	2.25%
Guarantee fee percentage (as percent)	1.40%
[1]	Text selection found with no content.

Related party transactions - De

Related party transactions - Debt Arrangements and Deferred Consideration Receivable (Details) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 19, 2015	May 31, 2013
Related Party Transaction [Line Items]
Share in results from associated companies (net of tax)		$ 174,000,000	$ 283,000,000	$ 192,000,000
Long-term debt		$ 8,701,000,000	9,608,000,000
Shareholders' ownership (as percent)		23.60%
Seadrill Partners LLC | Performance Guarantee
Related Party Transaction [Line Items]
Guarantees		$ 165,000,000	185,000,000
Seadrill Partners LLC | Financial Guarantee
Related Party Transaction [Line Items]
Guarantees		0	621,000,000
Seadrill Partners LLC | Nigeria | Custom Guarantee
Related Party Transaction [Line Items]
Guarantees		600,000	400,000
Secured Debt
Related Party Transaction [Line Items]
Long-term debt		5,581,000,000	6,450,000,000
Credit facility, Ship Finance International Loans, $420 facility | Secured Debt | Seadrill Partners LLC
Related Party Transaction [Line Items]
Debt, face amount		$ 420,000,000
Seadrill Operating LP
Related Party Transaction [Line Items]
Ownership interest (as percent)					42.00%
Equity Method Investee | Seadrill Partners LLC | Vendor Financing Loan
Related Party Transaction [Line Items]
Loans receivable, related parties						$ 109,500,000
Equity Method Investee | Seadrill Partners LLC | Vendor Financing Loan | LIBOR
Related Party Transaction [Line Items]
Loan receivable basis spread on variable rate (as percent)						5.00%
Seadrill Partners LLC | Credit Facility $143 million, Charter Financing Loan | Vendor Financing Loan
Related Party Transaction [Line Items]
Due from related parties	$ 143,000,000		39,000,000	143,000,000
Interest rate on related party debt (as percent)	0.56%
Due to related parties	$ 143,000,000		$ 39,000,000	$ 143,000,000
Debt instrument, interest rate (as percent)		0.56%

Related party transactions - Sh

Related party transactions - Ship Finance Transactions (Details) - USD ($)		Jun. 30, 2015	Jun. 28, 2013	Dec. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Total acquisition price		$ 4,000,000
Long-term debt due to related parties					$ 314,000,000	$ 330,000,000
Repayments of debt to related party					39,000,000	103,000,000	$ 0	[1]
Payments of ordinary dividends, noncontrolling Interest					0	7,000,000	14,000,000	[1]
Interest expense	[2]				285,000,000	412,000,000	415,000,000
Ship Finance International Ltd VIEs
Related Party Transaction [Line Items]
Lease costs on leased units					190,000,000	191,000,000	193,000,000
Affiliated Entity | Ship Finance International Ltd VIEs
Related Party Transaction [Line Items]
Long-term debt due to related parties					314,000,000	330,000,000
Repayments of debt to related party					$ 101,000,000
Interest rate on related party debt (as percent)					4.50%
Gross loans outstanding						415,000,000
Interest expense					$ 15,000,000	19,000,000	19,000,000
North Atlantic Drilling | Ship Finance International Ltd VIEs
Related Party Transaction [Line Items]
Contingent consideration arrangements, maximum			$ 600,000,000
Lease term			15 years
North Atlantic Drilling | Affiliated Entity | Ship Finance International Ltd VIEs
Related Party Transaction [Line Items]
Long-term debt due to related parties			$ 195,000,000	$ 125,000,000
Interest rate on related party debt (as percent)			4.50%
SFL West Polaris Limited
Related Party Transaction [Line Items]
Total acquisition price				$ 111,000,000
West Hercules | Ship Finance International Ltd VIEs
Related Party Transaction [Line Items]
Lease costs on leased units					56,000,000	57,000,000	55,000,000
West Taurus | Ship Finance International Ltd VIEs
Related Party Transaction [Line Items]
Lease costs on leased units					51,000,000	52,000,000	57,000,000
West Linus | Ship Finance International Ltd VIEs
Related Party Transaction [Line Items]
Lease costs on leased units					$ 83,000,000	$ 82,000,000	$ 81,000,000
West Linus | North Atlantic Drilling | Variable Interest Entity, Primary Beneficiary
Related Party Transaction [Line Items]
Contingent consideration arrangements, maximum			$ 600,000,000
Lease term			15 years
[1]	Text selection found with no content.
[2]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

Related party transactions - Me

Related party transactions - Metrogas, Frontline, and Seatankers Transactions (Details) - USD ($) $ in Millions		Mar. 06, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Short-term debt to related parties			$ 10	$ 83
Proceeds from debt to related party			0	0	$ 143	[1]
Long-term debt			8,701	9,608
Repayments of debt to related party			39	103	0	[1]
Net gain on debt extinguishment			19	47	8
Interest expense	[2]		285	412	415
Affiliated Entity | Metrogas
Related Party Transaction [Line Items]
Interest rate on related party debt (as percent)		7.50%
Subordinated loan from related party		$ 50			50
Affiliated Entity | Frontline
Related Party Transaction [Line Items]
Related party expense			3	3	4
Affiliated Entity | Seatankers Management Norway AS
Related Party Transaction [Line Items]
Related party expense			$ 2	$ 2	$ 1
[1]	Text selection found with no content.
[2]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

Related party transactions - Ar

Related party transactions - Archer Transactions (Details) $ / shares in Units, € in Millions, £ in Millions		May 27, 2017	Apr. 25, 2017USD ($)$ / shares	Mar. 06, 2015USD ($)	Feb. 05, 2014GBP (£)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2017NOK (kr)	Apr. 30, 2017USD ($)	Dec. 31, 2016EUR (€)	May 27, 2016USD ($)	Jul. 14, 2014USD ($)	Dec. 09, 2013EUR (€)	Jul. 31, 2013USD ($)	Mar. 07, 2013USD ($)
Related Party Transaction [Line Items]
Investment income, net	[1]					$ 60,000,000	$ 66,000,000	$ 67,000,000
Net gain on debt extinguishment						19,000,000	47,000,000	8,000,000
Maximum potential future payment						4,111,000,000	5,680,000,000
Revenues related party						$ 110,000,000	$ 100,000,000	$ 119,000,000
Archer Limited (Archer)
Related Party Transaction [Line Items]
Ownership interest (as percent)			31.89%			15.69%	39.72%	39.90%	15.69%		39.72%
Performance Guarantee
Related Party Transaction [Line Items]
Maximum potential future payment	[2],[3],[4]					$ 1,213,000,000	$ 1,403,000,000
Affiliated Entity | Metrogas
Related Party Transaction [Line Items]
Subordinated loan from related party				$ 50,000,000				$ 50,000,000
Payments to acquire loans receivable				51,000,000
Accrued commitment fee and interest				$ 1,000,000
Interest rate on related party debt (as percent)				7.50%
Commitment fee (as a percent)				1.00%
Net amount								$ 0
Convertible Subordinated Loan Receivable, Gain (Loss) on Conversion Option, Related Party						4,000,000
Equity Method Investee | Seabras Sapura Participacoes and Seabras Sapura Holdco [Member]
Related Party Transaction [Line Items]
Accrued commitment fee and interest						6,000,000	6,000,000
Equity Method Investee | Archer Limited (Archer)
Related Party Transaction [Line Items]
Subordinated loan from related party							58,000,000
Interest rate on related party debt (as percent)		10.00%	5.50%
Ownership interest (as percent)								39.89%
Receivable from shipyard												$ 75,000,000
Common stock threshold value for transition to equity method						0
Investment income, net						3,000,000	8,000,000	$ 3,000,000
Net gain on debt extinguishment						$ 1,000,000
Maximum potential future payment								250,000,000								$ 100,000,000
Guarantee fee percentage (as percent)						1.25%			1.25%
Notes receivable			$ 37,000,000
Convertible Subordinated Loan Receivable, Conversion Price, Related Party | $ / shares			$ 2.083
Convertible Subordinated Loan Receivable, Subscription Price Premium, Related Party			75.00%
SG&A expenses from transactions with related party						$ 100,000	1,000,000	4,000,000
Equity Method Investee | Archer Limited (Archer) | Guarantee Fees Reimbursed
Related Party Transaction [Line Items]
Revenues related party						800,000	3,900,000	$ 3,600,000
Equity Method Investee | Archer Limited (Archer) | Financial Guarantee
Related Party Transaction [Line Items]
Maximum potential future payment											€ 48.4		$ 20,000,000	€ 48.4
Guarantee fee percentage (as percent)													1.25%	1.25%	1.25%
Maximum additional potential future payment															$ 100,000,000
Guarantee outstanding						0	25,000,000
Amount extinguished										$ 25,000,000
Cash payment proposed for restructure of liability							28,000,000
Equity Method Investee | Archer Limited (Archer) | Property Lease Guarantee
Related Party Transaction [Line Items]
Maximum potential future payment | £					£ 10
Guarantee period					10 years
Guarantee outstanding						10,000,000	10,000,000
Equity Method Investee | Archer Limited (Archer) | Performance Guarantee
Related Party Transaction [Line Items]
Maximum potential future payment						8,000,000			kr 66,000,000
Equity Method Investee | Archer Limited | Financial Guarantee
Related Party Transaction [Line Items]
Guarantee outstanding						0	25,000,000
Amount extinguished										2,500,000
Equity Method Investee | Archer Norge AS | Financial Guarantee
Related Party Transaction [Line Items]
Guarantee outstanding						$ 0	$ 3,000,000
Amount extinguished										$ 300,000
Convertible Subordinated Debt | Equity Method Investee | Archer Limited (Archer)
Related Party Transaction [Line Items]
Due from related parties			$ 45,000,000
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".
[2]	Guarantees to Archer - Within guarantees provided to customers are guarantees provided on behalf of Archer of $8 million (2016: $8 million). There were no guarantees in favor of banks provided on behalf of Archer as at December 31, 2017 as these were settled during the year (2016: $253 million and EUR 24 million ($25 million)). Guarantees in favor of suppliers include guarantees on behalf of Archer of GBP 7 million ($10 million) (2016: GBP 8 million ($10 million)). As of December 31, 2016, we recognized a $28 million contingent liability to reflect the potential cash settlement of the guarantees. Refer to Note 30 "Related party transactions" for more information.
[3]	Guarantees to SeaMex - Within guarantees in favor of customers are guarantees provided on behalf of SeaMex of $30 million (2016: $30 million). Guarantees in favor of banks includes guarantees on behalf of SeaMex of nil (2016: $0 million). Refer to Note 30 "Related party transactions" for more information.
[4]	Guarantees to Seadrill Partners - Within guarantees in favor of customers are guarantees provided on behalf of Seadrill Partners of $165 million (2016: $185 million). After the insulation of Seadrill Partners from Seadrill in August 2017 there were no guarantees in favor of banks provided on behalf of Seadrill Partners (2016: $621 million). Guarantees in favor of suppliers includes guarantees on behalf of Seadrill Partners of $0.6 million (2016: $0.4 million). Refer to Note 30 "Related party transactions" for more information.

Related party transactions -169

Related party transactions - SeaMex Limited (Details)	Mar. 10, 2015USD ($)	Jul. 31, 2015USD ($)	Mar. 31, 2015USD ($)	Mar. 31, 2014facility	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)		Nov. 30, 2016USD ($)
Related Party Transaction [Line Items]
Debt outstanding					$ 8,701,000,000	$ 9,608,000,000
Additional investment in equity method investment					0	16,000,000	$ 210,000,000	[1]
Maximum guarantee					4,111,000,000	5,680,000,000
SeaMex Limited
Related Party Transaction [Line Items]
Consideration receivable	$ 162,000,000	$ 162,000,000
Equity Method Investee | SeaMex Limited
Related Party Transaction [Line Items]
Interest income, related party					28,000,000	18,000,000	17,000,000
Outstanding balance							51,000,000
Equity Method Investee | SeaMex Limited | Drilling units
Related Party Transaction [Line Items]
Maximum guarantee					30,000,000	30,000,000
Equity Method Investee | Unsecured bonds | SeaMex Limited
Related Party Transaction [Line Items]
Loans receivable, related parties					$ 20,000,000
Percentage contribution of facility to related party					50.00%
Equity Method Investee | Unsecured bonds | LIBOR | SeaMex Limited
Related Party Transaction [Line Items]
Loan receivable basis spread on variable rate (as percent)					6.50%
Equity Method Investee | SeaMex Limited
Related Party Transaction [Line Items]
Management service agreement termination notice period					60 days
Other revenues					$ 9,000,000	7,000,000	11,000,000
Debt, face amount			$ 250,000,000
Number of credit facilities | facility				2
Debt outstanding					250,000,000	250,000,000
Accrued interest forgiven							10,000,000
Loan to related party					$ 45,000,000		45,000,000		$ 45,000,000
Equity Method Investee | SeaMex Limited | LIBOR
Related Party Transaction [Line Items]
Loan receivable basis spread on variable rate (as percent)									6.50%
Equity Method Investee | SeaMex Limited | Revolving Credit Facility
Related Party Transaction [Line Items]
Debt, face amount			20,000,000
Equity Method Investee | SeaMex Limited | Medium-term Notes
Related Party Transaction [Line Items]
Debt, face amount			$ 230,000,000
Equity Method Investee | SeaMex Limited | Medium-term Notes | LIBOR
Related Party Transaction [Line Items]
Basis spread on variable rate (as percent)			6.50%
Equity Method Investee | Seadrill Jack Up Operations De Mexico
Related Party Transaction [Line Items]
Ownership (as percent)					100.00%
Equity Method Investee | Seadrill Jack Up Operations De Mexico | Vessel and rig operating expenses
Related Party Transaction [Line Items]
Related party expense					$ (5,000,000)	(5,000,000)	(10,000,000)
Equity Method Investee | Sapura
Related Party Transaction [Line Items]
Interest income, related party					$ 4,000,000	$ 2,100,000	1,500,000
Equity Method Investee | Fintech
Related Party Transaction [Line Items]
Additional investment in equity method investment							$ 19,000,000
Ownership interest (as percent)							50.00%
Minimum | Equity Method Investee
Related Party Transaction [Line Items]
Management fee (as percent)					4.50%
Minimum | Equity Method Investee | Seadrill Jack Up Operations De Mexico
Related Party Transaction [Line Items]
Management fee (as percent)					4.85%
Maximum | Equity Method Investee
Related Party Transaction [Line Items]
Management fee (as percent)					8.00%
Maximum | Equity Method Investee | Seadrill Jack Up Operations De Mexico
Related Party Transaction [Line Items]
Management fee (as percent)					8.00%
[1]	Text selection found with no content.

Related party transactions -170

Related party transactions - SeaMex Receivables and Payables (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Seller’s credit	$ 547	$ 523
SeaMex Limited | Equity Method Investee
Related Party Transaction [Line Items]
Seller’s credit	250	250
$45 million loan facility	45		$ 45	$ 45
Interest Receivable, Related Party	50	22
Other payables	(3)	(2)
SeaMex Limited | Equity Method Investee | Other Receivables
Related Party Transaction [Line Items]
Other receivables	$ 32	$ 31

Related party transactions -171

Related party transactions - Seabras Sapura transactions (Details) € in Thousands		Dec. 30, 2015USD ($)	Dec. 31, 2016USD ($)	Oct. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Apr. 30, 2015USD ($)	Jan. 31, 2015USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	May 31, 2014USD ($)	May 31, 2014EUR (€)	Nov. 30, 2012USD ($)
Related Party Transaction [Line Items]
Maximum guarantee			$ 5,680,000,000						$ 4,111,000,000	$ 5,680,000,000
Vessel and rig operating expenses	[1]								$ 792,000,000	1,015,000,000	$ 1,611,000,000
Sapura | Equity Method Investee
Related Party Transaction [Line Items]
Maximum exposure ratio									50.00%
Interest income, related party									$ 4,000,000	2,100,000	1,500,000
Seabras Sapura Joint Venture | Seabras Sapura, May 2014 Loan One | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable			11,000,000						11,000,000	11,000,000		$ 10,800,000
Loan receivable basis spread on variable rate (as percent)												3.40%	3.40%
Seabras Sapura Joint Venture | Seabras Sapura, May 2014 Loan Two | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable			0						0	0		$ 4,500,000	€ 3,250
Loan receivable basis spread on variable rate (as percent)												3.40%	3.40%
Seabras Sapura Joint Venture | Seabras Sapura, January 2015 Loan | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable			18,000,000				$ 18,000,000		18,000,000	18,000,000
Interest rate on related party debt (as percent)							3.40%
Seabras Sapura Joint Venture | Seabras Sapura, April 2015 Loan | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable			14,000,000			$ 14,000,000			14,000,000	14,000,000
Seabras Sapura Joint Venture | Seabras Sapura, April 2015 Loan | LIBOR | Equity Method Investee
Related Party Transaction [Line Items]
Interest rate on related party debt (as percent)						3.99%
Seabras Sapura Joint Venture | Seabras Sapura December 2015 Loan | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable		$ 3,300,000	3,300,000						3,300,000	3,300,000
Interest rate on related party debt (as percent)		4.40%
Seabras Sapura Joint Venture | Seabras Sapura, June 2016 Loan | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable			13,600,000		$ 14,000,000				14,000,000	13,600,000
Seabras Sapura Joint Venture | Seabras Sapura, June 2016 Loan | LIBOR | Equity Method Investee
Related Party Transaction [Line Items]
Interest rate on related party debt (as percent)					3.99%
Seabras Sapura Joint Venture | Seabras Sapura, October 2016 Loan | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable			12,000,000	$ 12,000,000					12,000,000	12,000,000
Seabras Sapura Joint Venture | Seabras Sapura, October 2016 Loan | LIBOR | Equity Method Investee
Related Party Transaction [Line Items]
Interest rate on related party debt (as percent)				3.99%
Seabras Sapura Joint Venture | Seabras Sapura, December 2016 Loan One | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable			6,000,000						6,000,000	$ 6,000,000
Seabras Sapura Joint Venture | Seabras Sapura, December 2016 Loan One | LIBOR | Equity Method Investee
Related Party Transaction [Line Items]
Interest rate on related party debt (as percent)										3.99%
Seabras Sapura Joint Venture | Seabras Sapura, December 2016 Loan Two | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable			$ 7,000,000						7,000,000	$ 7,000,000
Interest rate on related party debt (as percent)			4.50%
Seabras Sapura Joint Venture | Seabras Sapura, December 2016 Loan Three | Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable			$ 7,000,000						7,000,000	7,000,000
Interest rate on related party debt (as percent)			4.50%
Seabras Sapura | Equity Method Investee
Related Party Transaction [Line Items]
Interest receivable			$ 6,000,000						6,000,000	6,000,000
Seabras Sapura | Equity Method Investee | Spain
Related Party Transaction [Line Items]
Vessel and rig operating expenses	[1]								$ 1,000,000	$ 2,000,000	$ 1,000,000
Seabras Sapura Participacoes
Related Party Transaction [Line Items]
Ownership interest (as percent)			50.00%						50.00%	50.00%	50.00%
Ownership percentage held by equity method investee (as percent)									50.00%
Seabras Sapura Holding
Related Party Transaction [Line Items]
Ownership interest (as percent)			50.00%						50.00%	50.00%	50.00%
Ownership percentage held by equity method investee (as percent)									50.00%
Seabras Sapura Holding | Financial Guarantee
Related Party Transaction [Line Items]
Maximum additional potential future payment			$ 0						$ 0	$ 0
Seabras Sapura Joint Venture | Secured Debt
Related Party Transaction [Line Items]
Maximum exposure ratio						50.00%		50.00%
Maximum borrowing capacity								$ 543,000,000
Maximum guarantee			367,000,000						$ 328,000,000	367,000,000
Guarantee period for debt service coverage									6 months
Guarantee period for operating expenses									3 months
Seabras Sapura Joint Venture | Sapura Diamante and Sapura Topazio | Secured Debt
Related Party Transaction [Line Items]
Maximum guarantee			218,000,000						$ 186,000,000	218,000,000
Seabras Sapura Joint Venture | Sapura Onix, Sapura Jade, and Supra Rubi | Secured Debt
Related Party Transaction [Line Items]
Maximum borrowing capacity						$ 780,000,000
Maximum guarantee			0						0	0
Seabras Sapura Joint Venture | Sapura Esmeralda | Secured Debt
Related Party Transaction [Line Items]
Maximum borrowing capacity								$ 36,000,000						$ 179,000,000
Maximum guarantee			$ 202,000,000						$ 184,000,000	$ 202,000,000
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

Related party transactions - Ot

Related party transactions - Other related party transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transactions [Abstract]
Revenues related party	$ 110	$ 100	$ 119

Risk management and financia173

Risk management and financial instruments (Restated) - Realized and Unrealized Gains and Losses (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss on derivative financial instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain / (loss) on derivative financial instruments	$ 11,000,000	$ (74,000,000)	$ (150,000,000)
Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate contracts not designated as instrument hedging	(30,000,000)	(48,000,000)	(104,000,000)
Interest Rate Swap | Loss on derivative financial instruments
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate contracts not designated as instrument hedging	(31,000,000)	(48,000,000)	(104,000,000)
Cross currency interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate contracts not designated as instrument hedging	46,000,000	(20,000,000)	(7,000,000)
Cross currency interest rate swaps | Loss on derivative financial instruments
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate contracts not designated as instrument hedging	46,000,000	(20,000,000)	(7,000,000)
Foreign currency forwards
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate contracts not designated as instrument hedging	0	0	(9,000,000)
Foreign currency forwards | Loss on derivative financial instruments
Derivative Instruments, Gain (Loss) [Line Items]
Foreign currency forwards not qualified as hedge accounting	1,000,000	0	(9,000,000)
TRS agreements | Loss on derivative financial instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain / (loss) on derivative financial instruments	0	(6,000,000)	(27,000,000)
Other | Loss on derivative financial instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain / (loss) on derivative financial instruments	$ (5,000,000)	$ 0	$ (3,000,000)

Risk management and financia174

Risk management and financial instruments (Restated) - Narrative (Details) kr / shares in Units, $ / shares in Units, kr in Millions	Sep. 05, 2016$ / sharesshares	Sep. 05, 2016kr / sharesshares	Apr. 27, 2016USD ($)	Nov. 06, 2015USD ($)kr / sharesshares	Jul. 08, 2015USD ($)	Jun. 30, 2015USD ($)shares	Feb. 06, 2015NOK (kr)kr / sharesshares	Dec. 31, 2014kr / shares	Sep. 18, 2013USD ($)contract	Dec. 31, 2017USD ($)shares	Dec. 31, 2017USD ($)kr / sharesshares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)shares		Sep. 13, 2017USD ($)	Apr. 30, 2013USD ($)
Derivative [Line Items]
Total debt principal										$ 7,705,000,000	$ 7,705,000,000	$ 0
Derivatives previously recorded at fair value										249,000,000	249,000,000
Embedded derivative, loss on embedded derivative										4,000,000
Fair value gain on loans receivable										1,000,000
Convertible debt, fair value disclosures										52,000,000	52,000,000
Debt outstanding										8,701,000,000	8,701,000,000	9,608,000,000
Interest paid, net of capitalized interest										264,000,000		400,000,000	$ 458,000,000	[1]
Net gain on debt extinguishment										19,000,000		47,000,000	8,000,000
Option agreement, strike price (in NOK per share) | $ / shares	$ 20.30
Fair value of the consideration received						$ 4,000,000
Derivative, collateral, right to reclaim cash					$ 93,000,000
Cash and restricted cash										104,000,000	104,000,000	75,000,000
Marketable securities pledged as collateral										$ 0	$ 0	$ 0
Weighted average cost of capital (as percent)												10.00%
Sevan Drilling
Derivative [Line Items]
Restructuring and related activities, ratio of distributed shares from previous to current entity										2000.00%
Ship Finance Variable Interest Entities
Derivative [Line Items]
Weighted average cost of capital (as percent)										11.00%
Strike Price 1 | Sevan Drilling
Derivative [Line Items]
Option agreement (in shares) | shares				10,803,274
Option agreement, strike price (in NOK per share) | kr / shares				kr 8.9482
Strike Price 2 | Sevan Drilling
Derivative [Line Items]
Option agreement (in shares) | shares				4,091,425
Option agreement, strike price (in NOK per share) | kr / shares											$ 8.5539
Interest Rate Contract [Member]
Derivative [Line Items]
Outstanding principal amount												$ (230,000,000)
Effect of 1% interest rate increase on net income										$ 2,100,000		3,000,000
Effect of 1% interest rate decrease on net income										3,000,000		5,000,000
Interest Rate Contract [Member] | Affiliated Entity
Derivative [Line Items]
Outstanding principal amount										(9,900,000,000)	$ (9,900,000,000)
Interest Rate Swap
Derivative [Line Items]
Derivatives previously recorded at fair value										39,000,000	39,000,000				$ 18,000,000
Outstanding principal amount										(5,675,000,000)	(5,675,000,000)	(6,372,000,000)
Gross liability												(64,000,000)
Net liability												(41,000,000)
Derivative asset												4,000,000
Interest rate contracts not designated as instrument hedging										(30,000,000)		(48,000,000)	(104,000,000)
Interest Rate Swap | Variable Interest Entity, Primary Beneficiary
Derivative [Line Items]
Other comprehensive income, unrealized gain (loss) on interest rate swaps in VIEs										1,200,000		1,100,000
Interest paid, net of capitalized interest										1,000,000		2,000,000
Net gain (loss) on fair value hedge ineffectiveness										0		0	0
Interest Rate Swap | Variable Interest Entity, Primary Beneficiary | Other Noncurrent Liabilities | Ship Finance Variable Interest Entities
Derivative [Line Items]
Gross liability										0	0	(1,000,000)
Interest Rate Swap 2
Derivative [Line Items]
Outstanding principal amount										$ (150,000,000)	$ (150,000,000)	(162,000,000)
Derivative, fixed interest rate (as percent)										2.12%	2.12%
Floating Interest Rate and Cross Currency Interest Rate Contract [Member]
Derivative [Line Items]
Outstanding principal amount										$ (7,400,000,000)	$ (7,400,000,000)
Cross currency interest rate swaps
Derivative [Line Items]
Derivatives previously recorded at fair value										210,000,000	210,000,000				$ 71,000,000
Outstanding principal amount												(807,000,000)
Gross liability												(194,000,000)
Interest rate contracts not designated as instrument hedging										46,000,000		(20,000,000)	(7,000,000)
Effect of 1% exchange rate on gain (loss) on derivatives										(5,500,000)
Cross currency interest rate swaps | Original, Prior to being Retranslated
Derivative [Line Items]
Outstanding principal amount										(807,000,000)	(807,000,000)
Fixed Interest Rate Swap
Derivative [Line Items]
Outstanding principal amount										(2,270,000,000)	(2,270,000,000)
Foreign currency forwards
Derivative [Line Items]
Gross liability										0	$ 0	0
Interest rate contracts not designated as instrument hedging										0		0	(9,000,000)
Effect of 1% exchange rate on gain (loss) on derivatives										$ 5,400,000
TRS agreements
Derivative [Line Items]
Option agreement (in shares) | shares	4,000,000	4,000,000								0	0
Option agreement, strike price (in NOK per share) | kr / shares		kr 20.30
Derivative instruments not designated as hedging instruments, gain (loss), net										$ 0		(6,000,000)	$ (27,000,000)
Sevan Share Repurchase Agreement | Sevan Drilling ASA
Derivative [Line Items]
Stock repurchase program, number of shares authorized to be repurchased (in shares) | shares						297,893,964
Sevan Share Repurchase Agreement | Sevan Drilling
Derivative [Line Items]
Stock repurchase program, number of shares authorized to be repurchased (in shares) | shares						14,894,699
Sevan Share Repurchase Agreement | Sevan Drilling ASA
Derivative [Line Items]
Option indexed to issuer's equity, settlement alternatives, cash, at fair value | kr							kr 135
Sevan Share Repurchase Agreement | Strike Price 1 | Sevan Drilling ASA
Derivative [Line Items]
Option agreement (in shares) | shares							216,065,464						216,065,464
Option agreement, strike price (in NOK per share) | kr / shares							kr 0.6247	kr 4.1701
Sevan Share Repurchase Agreement | Strike Price 2 | Sevan Drilling ASA
Derivative [Line Items]
Option agreement (in shares) | shares							81,828,500
Option agreement, strike price (in NOK per share) | kr / shares							kr 0.6243	kr 4.1966
Sevan Share Repurchase Agreement | Other Current Liabilities
Derivative [Line Items]
Associated liabilities				kr 16,000,000
SapuraKencana Share Agreements
Derivative [Line Items]
Derivative, fixed interest rate (as percent)					2.60%
Number of instruments held | contract									2
Proceeds from derivative instrument, financing activities									$ 250,000,000
Derivative, term of contract (in years)									3 years
Description of variable rate basis									LIBOR
Derivative, basis spread on variable rate (as percent)									1.90%
Proceeds from derivative instrument, financing activities, reduction in proceeds received					$ 90,000,000
Cash and restricted cash					160,000,000
SapuraKencana Share Agreements | Other Noncurrent Liabilities
Derivative [Line Items]
Proceeds from derivative instrument, financing activities					$ 160,000,000
Minimum | Interest Rate Swap
Derivative [Line Items]
Derivative maturity date										Nov. 2, 2017
Derivative, fixed interest rate (as percent)										0.74%	0.74%
Minimum | Cross currency interest rate swaps
Derivative [Line Items]
Derivative maturity date										Mar. 1, 2018
Derivative, fixed interest rate (as percent)										4.94%	4.94%
Maximum | Interest Rate Swap
Derivative [Line Items]
Derivative maturity date										Jan. 29, 2027
Derivative, fixed interest rate (as percent)										3.34%	3.34%
Maximum | Cross currency interest rate swaps
Derivative [Line Items]
Derivative maturity date										Mar. 1, 2019
Derivative, fixed interest rate (as percent)										6.1825%	6.1825%
Archer Limited (Archer)
Derivative [Line Items]
Subordinated loan												37,000,000
Loans payable												45,000,000
Loans payable fair value												56,000,000
Net gain on debt extinguishment										$ 19,000,000
Secured Debt
Derivative [Line Items]
Debt outstanding										5,581,000,000	$ 5,581,000,000	6,450,000,000
Secured Debt | $360 facility (Asia Offshore Drilling)
Derivative [Line Items]
Debt outstanding										210,000,000	210,000,000	237,000,000
Debt, face amount										360,000,000	360,000,000					$ 360,000,000
Unsecured bonds
Derivative [Line Items]
Total debt principal										5,371,000,000	5,371,000,000
Fair value
Derivative [Line Items]
Long-term floating rate debt (including the current portion)												6,542,000,000
Fixed interest bonds, fair value disclosures, noncurrent												766,000,000
Floating interest bonds - long term												223,000,000
Related party fixed rate debt - long term										218,000,000	218,000,000	242,000,000
Carrying value
Derivative [Line Items]
Long-term floating rate debt (including the current portion)										6,367,000,000	6,367,000,000	7,333,000,000
Fixed interest bonds, fair value disclosures, noncurrent										1,735,000,000	1,735,000,000	1,735,000,000
Floating interest bonds - long term										599,000,000	599,000,000	540,000,000
Related party fixed rate debt - long term										$ 314,000,000	$ 314,000,000	$ 415,000,000
SapuraKencana
Derivative [Line Items]
Debt collateral amount													$ 195,000,000
Proceeds from available-for-sale securities			$ 195,000,000
[1]	Text selection found with no content.

Risk management and financia175

Risk management and financial instruments (Restated) - By Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Interest Rate Swap
Derivative [Line Items]
Total	$ 5,675	$ 6,372

Risk management and financia176

Risk management and financial instruments (Restated) - Cross Currency Swap Positions (Details) - Cross currency interest rate swaps - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Total		$ 807
Original, Prior to being Retranslated
Derivative [Line Items]
Total	$ 807

Risk management and financia177

Risk management and financial instruments (Restated) - Variable Interest Entities (Details) - Interest Rate Swap - Variable Interest Entity, Primary Beneficiary $ in Millions	Dec. 31, 2017USD ($)
Mar 2014 - Oct 2018
Derivative [Line Items]
Outstanding principal	$ 4
Pay rate (as percent)	2.014%
Mar 2014 - Nov 2018
Derivative [Line Items]
Outstanding principal	$ 4
Pay rate (as percent)	2.014%
Dec 2013 - Dec 2018
Derivative [Line Items]
Outstanding principal	$ 144.5
Pay rate (as percent)	1.7725%

Risk management and financia178

Risk management and financial instruments (Restated) - Fair Value of Financial Instruments Table (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 1,255	$ 1,368
Restricted cash	104	75
Related party loans receivable - short term	25	174
Related party loans receivable - long term	522	487
Long-term floating rate debt (including the current portion)		6,542
Floating interest bonds - long term		223
Related party fixed rate debt - long term	218	242
Carrying value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,255	1,368
Restricted cash	104	75
Related party loans receivable - short term	25	174
Related party loans receivable - long term	515	487
Long-term floating rate debt (including the current portion)	6,367	7,333
Floating interest bonds - long term	599	540
Related party fixed rate debt - long term	$ 314	$ 415

Risk management and financia179

Risk management and financial instruments (Restated) - Fair Value Measurements of Recurring Assets and Liabilities (Details) - Fair value, recurring basis - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities - current asset	$ 124	$ 110
Total assets	176	114
Total liabilities		236
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities - current asset	124	110
Total assets	124	110
Total liabilities		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities - current asset	0	0
Total assets	0	4
Total liabilities		236
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities - current asset	0	0
Total assets	52	0
Total liabilities		0
Interest Rate Swap | Short-term payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		41
Interest Rate Swap | Short-term payable | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		0
Interest Rate Swap | Short-term payable | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		41
Interest Rate Swap | Short-term payable | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		0
Interest Rate Swap | Long-term payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		1
Interest Rate Swap | Long-term payable | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		0
Interest Rate Swap | Long-term payable | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		1
Interest Rate Swap | Long-term payable | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		0
Cross currency interest rate swaps | Short-term payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		194
Cross currency interest rate swaps | Short-term payable | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		0
Cross currency interest rate swaps | Short-term payable | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		194
Cross currency interest rate swaps | Short-term payable | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts, payable		0
Short Term Receivable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt instrument - non-current asset	52
Short Term Receivable | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt instrument - non-current asset	0
Short Term Receivable | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt instrument - non-current asset	0
Short Term Receivable | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt instrument - non-current asset	$ 52
Non-current assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts – non-current assets		4
Non-current assets | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts – non-current assets		0
Non-current assets | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts – non-current assets		4
Non-current assets | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap contracts – non-current assets		$ 0

Risk management and financia180

Risk management and financial instruments (Restated) - Retained Risk (Details)	12 Months Ended
	Dec. 31, 2017USD ($)
Uninsured Risk
Loss Contingencies [Line Items]
Self insured retention period	60 days
Loss from Catastrophes
Loss Contingencies [Line Items]
Insurance combined single limit	$ 100,000,000
Minimum | Uninsured Risk
Loss Contingencies [Line Items]
Self insurance, quota share on loss of hire daily amount, percent	75.00%
Maximum | Uninsured Risk
Loss Contingencies [Line Items]
Compensation period	290 days
Self insurance, quota share on loss of hire daily amount, percent	100.00%
Physical Damage Insurance | Uninsured Risk
Loss Contingencies [Line Items]
Amount of deductible (maximum amount)	$ 5,000,000
Protection and Indemnity Insurance | Uninsured Risk
Loss Contingencies [Line Items]
Amount of deductible (maximum amount)	25,000
Protection and Indemnity Insurance | Insurance Claims | United States
Loss Contingencies [Line Items]
Amount of deductible (maximum amount)	500,000
Protection and Indemnity Insurance | Maximum | Insurance Claims
Loss Contingencies [Line Items]
Amount of deductible (maximum amount)	$ 750,000,000

Commitments and contingencies -

Commitments and contingencies - Legal Proceedings and Purchase Commitments (Details)	Mar. 13, 2017USD ($)	Jul. 23, 2015USD ($)	Jan. 31, 2017USD ($)	Dec. 31, 2017USD ($)rigcontract	Dec. 31, 2016USD ($)	Jan. 31, 2015drilling_unit
Purchase Commitment [Line Items]
Assets pledged under mortgages and overdraft facilities				$ 12,933,000,000	$ 13,927,000,000
Marketable securities pledged as collateral				$ 0	0
Number of newbuilding contracts | contract				9
Number of new building contracts for jack up rigs | rig				8
Maturity schedule for contractual commitments [Abstract]
2,018				$ 1,685,000,000
2,019				0
2,020				0
2,021				0
2,022				0
2023 and thereafter				0
Purchase commitments				1,685,000,000	4,098,000,000
Sevan Drilling ASA
Maturity schedule for contractual commitments [Abstract]
Purchase commitments				526,000,000	480,000,000
Cancellation of West Mira | Drilling units
Purchase Commitment [Line Items]
Newbuilding settlement claim	$ 170,000,000
Rosneft Transaction
Purchase Commitment [Line Items]
Loss contingency, estimated backlog of transaction		$ 4,100,000,000
Customer Claims | North Atlantic Drilling
Purchase Commitment [Line Items]
Settlement award			$ 34,700,000
Offshore Workers' Pension Case | North Atlantic Drilling
Purchase Commitment [Line Items]
Loss contingency recognized				$ 0	$ 0
Patent Infringement
Purchase Commitment [Line Items]
Number of drilling rigs | drilling_unit						1

Commitments and contingencie182

Commitments and contingencies - Guarantees (Details) € in Millions, £ in Millions

12 Months Ended

Dec. 31, 2016USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2017NOK (kr)

Dec. 31, 2017GBP (£)

[2]

Dec. 31, 2016GBP (£)

Dec. 31, 2016EUR (€)

Dec. 31, 2015USD ($)

Jul. 14, 2014USD ($)

Dec. 09, 2013EUR (€)

Mar. 07, 2013USD ($)

Guarantor Obligations [Line Items]

Maximum guarantee

$ 5,680,000,000

$ 4,111,000,000

Archer Limited (Archer) | Equity Method Investee

Guarantor Obligations [Line Items]

Maximum guarantee

$ 250,000,000

$ 100,000,000

Performance Guarantee

Guarantor Obligations [Line Items]

Maximum guarantee

[1],[2],[3]

1,403,000,000

1,213,000,000

Performance Guarantee | Archer Limited (Archer) | Equity Method Investee

Guarantor Obligations [Line Items]

Maximum guarantee

8,000,000

kr 66,000,000

Performance Guarantee | Archer Limited

Guarantor Obligations [Line Items]

Maximum guarantee

8,000,000

8,000,000

Performance Guarantee | Seadrill Partners LLC

Guarantor Obligations [Line Items]

Guarantee outstanding

185,000,000

165,000,000

Performance Guarantee | SeaMex Limited

Guarantor Obligations [Line Items]

Guarantee outstanding

30,000,000

30,000,000

Guarantee in favor of banks

Guarantor Obligations [Line Items]

Maximum guarantee

[1],[2],[3],[4]

1,677,000,000

698,000,000

Guarantee in favor of banks | Archer Limited

Guarantor Obligations [Line Items]

Maximum guarantee

253,000,000

€ 24

Guarantee in favor of banks | Archer Limited | Euro Member Countries, Euro

Guarantor Obligations [Line Items]

Maximum guarantee

25,000,000

Guarantee in favor of banks | Seabras Sapura

Guarantor Obligations [Line Items]

Maximum guarantee

787,000,000

698,000,000

Guarantee in favor of suppliers

Guarantor Obligations [Line Items]

Maximum guarantee

[1],[3],[4]

2,600,000,000

2,200,000,000

Guarantee in favor of suppliers | Archer Limited

Guarantor Obligations [Line Items]

Maximum guarantee

10,000,000

10,000,000

[2]

£ 7

£ 8

Guarantee in favor of suppliers | Seabras Sapura Holding

Guarantor Obligations [Line Items]

Maximum guarantee

0

0

Financial Guarantee | Archer Limited (Archer) | Equity Method Investee

Guarantor Obligations [Line Items]

Maximum guarantee

€ 48.4

$ 20,000,000

€ 48.4

Guarantee outstanding

25,000,000

0

Cash payment proposed for restructure of liability

28,000,000

Financial Guarantee | Seadrill Partners LLC

Guarantor Obligations [Line Items]

Guarantee outstanding

621,000,000

0

Financial Guarantee | SeaMex Limited

Guarantor Obligations [Line Items]

Guarantee outstanding

0

0

Custom Guarantee | Nigeria | Seadrill Partners LLC

Guarantor Obligations [Line Items]

Guarantee outstanding

$ 400,000

$ 600,000

[1]

Guarantees to Archer - Within guarantees provided to customers are guarantees provided on behalf of Archer of $8 million (2016: $8 million). There were no guarantees in favor of banks provided on behalf of Archer as at December 31, 2017 as these were settled during the year (2016: $253 million and EUR 24 million ($25 million)). Guarantees in favor of suppliers include guarantees on behalf of Archer of GBP 7 million ($10 million) (2016: GBP 8 million ($10 million)). As of December 31, 2016, we recognized a $28 million contingent liability to reflect the potential cash settlement of the guarantees. Refer to Note 30 "Related party transactions" for more information.

[2]

Guarantees to SeaMex - Within guarantees in favor of customers are guarantees provided on behalf of SeaMex of $30 million (2016: $30 million). Guarantees in favor of banks includes guarantees on behalf of SeaMex of nil (2016: $0 million). Refer to Note 30 "Related party transactions" for more information.

[3]

Guarantees to Seadrill Partners - Within guarantees in favor of customers are guarantees provided on behalf of Seadrill Partners of $165 million (2016: $185 million). After the insulation of Seadrill Partners from Seadrill in August 2017 there were no guarantees in favor of banks provided on behalf of Seadrill Partners (2016: $621 million). Guarantees in favor of suppliers includes guarantees on behalf of Seadrill Partners of $0.6 million (2016: $0.4 million). Refer to Note 30 "Related party transactions" for more information.

[4]

Guarantees to Seabras Sapura -Within guarantees in favor of banks are guarantees provided on behalf of Seabras Sapura Participacoes and Seabras Sapura Holdco totaling $698 million (2016: $787 million). There were no guarantees in favor of suppliers in relation to our joint venture Seabras Sapura Holdco (2016: nil). Refer to Note 30 "Related party transactions" for more information.

Operating leases (Details)

Operating leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases, Operating [Abstract]
Rent expense	$ 19	$ 17	$ 23
Operating leases, future minimum payments due, fiscal year maturity [Abstract]
2,018	12
2,019	8
2,020	7
2,021	7
2,022	5
2023 and thereafter	1
Total	$ 40

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details)	Jun. 28, 2013USD ($)	Dec. 31, 2017USD ($)rig	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	[1]	Dec. 31, 2014USD ($)
Sale Leaseback Transaction [Line Items]
Cash and cash equivalents		$ 1,255,000,000	$ 1,368,000,000	$ 1,044,000,000		$ 831,000,000	[1]
Number of semi submersible rigs under sale leaseback arrangements | rig		2
Term of lease contracts		15 years
Long-term debt due to related parties		$ 314,000,000	330,000,000
Amount due from related parties - current		217,000,000	376,000,000
Short-term debt to related parties		10,000,000	83,000,000
SFL Linus Limited
Sale Leaseback Transaction [Line Items]
Repurchase obligation		100,000,000
Variable Interest Entity, Primary Beneficiary
Sale Leaseback Transaction [Line Items]
Cash and cash equivalents		17,000,000	0
Dividend to non-controlling interests in VIEs		14,000,000	113,000,000
Variable Interest Entity, Primary Beneficiary | North Atlantic Drilling | SFL Linus Limited
Sale Leaseback Transaction [Line Items]
Contingent consideration arrangements, maximum	$ 600,000,000
Lease term	15 years
Affiliated Entity | Ship Finance International Ltd VIEs
Sale Leaseback Transaction [Line Items]
Long-term debt due to related parties		$ 314,000,000	330,000,000
Interest rate on related party debt (as percent)		4.50%
Affiliated Entity | Ship Finance International Ltd VIEs | North Atlantic Drilling
Sale Leaseback Transaction [Line Items]
Long-term debt due to related parties	$ 195,000,000					$ 125,000,000
Interest rate on related party debt (as percent)	4.50%
Affiliated Entity | SFL Deepwater Limited
Sale Leaseback Transaction [Line Items]
Amount due from related parties - current			26,000,000
Short-term debt to related parties		$ 0
Affiliated Entity | SFL Hercules Ltd
Sale Leaseback Transaction [Line Items]
Amount due from related parties - current			$ 59,000,000
[1]	Text selection found with no content.

Variable Interest Entities - Su

Variable Interest Entities - Summary of Sale and Leaseback Arrangements (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
West Taurus
Variable Interest Entity [Line Items]
Sale value (In US$ millions)	$ 850
First repurchase option (In US$ millions)	418
Last repurchase option (1) (In US$ millions)	149	[1]
SFL Hercules Limited
Variable Interest Entity [Line Items]
Sale value (In US$ millions)	850
First repurchase option (In US$ millions)	580
Last repurchase option (1) (In US$ millions)	135	[1]
SFL Linus Limited
Variable Interest Entity [Line Items]
Sale value (In US$ millions)	600
First repurchase option (In US$ millions)	370
Last repurchase option (1) (In US$ millions)	170	[1]
Repurchase obligation	$ 100
[1]	Ship Finance has a right to require us to purchase the West Linus rig on the 15th anniversary for the price of $100 million if we don’t exercise the final repurchase option.

Variable Interest Entities -186

Variable Interest Entities - Summary of Average Bareboat Charter Rates per Day (Details) $ / d in Thousands	Dec. 31, 2017$ / d
West Taurus
Sale Leaseback Transaction [Line Items]
2,017	158
2,018	158
2,019	144
2,020	143
2,021	136
2,022	135
SFL Hercules Limited
Sale Leaseback Transaction [Line Items]
2,017	170
2,018	166
2,019	143
2,020	141
2,021	135
2,022	135
SFL Linus Limited
Sale Leaseback Transaction [Line Items]
2,017	222
2,018	222
2,019	173
2,020	140
2,021	140
2,022	133

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities in Statutory Accounts of VIEs (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	[1]	Dec. 31, 2014	[1]
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 1,255,000,000	$ 1,368,000,000	$ 1,044,000,000		$ 831,000,000
Book value of units in the Company's consolidated accounts	[2]	13,216,000,000	12,853,000,000
Amount due from related parties - current		217,000,000	376,000,000
Amounts due to related parties - current		10,000,000	83,000,000
SFL Deepwater Limited
Variable Interest Entity [Line Items]
Investment in finance lease		335,000,000	365,000,000
Amount due from related parties		4,000,000	4,000,000
Other assets (1)		6,000,000	2,000,000
Total assets		345,000,000	371,000,000
Short-term interest bearing debt		226,000,000	23,000,000
Long-term interest bearing debt		0	226,000,000
Other liabilities		3,000,000	3,000,000
Short-term debt due to related parties		0	0
Long-term debt due to related parties (2)	[3]	113,000,000	119,000,000
Total liabilities		342,000,000	371,000,000
Equity		3,000,000	0
Book value of units in the Company's consolidated accounts		385,000,000	409,000,000
SFL Hercules Limited
Variable Interest Entity [Line Items]
Investment in finance lease		326,000,000	360,000,000
Amount due from related parties		4,000,000	4,000,000
Other assets (1)		6,000,000	2,000,000
Total assets		336,000,000	366,000,000
Short-term interest bearing debt		27,000,000	28,000,000
Long-term interest bearing debt		224,000,000	251,000,000
Other liabilities		2,000,000	1,000,000
Short-term debt due to related parties		0	0
Long-term debt due to related parties (2)	[3]	80,000,000	86,000,000
Total liabilities		333,000,000	366,000,000
Equity		3,000,000	0
Book value of units in the Company's consolidated accounts		508,000,000	537,000,000
SFL Linus Limited
Variable Interest Entity [Line Items]
Investment in finance lease		431,000,000	483,000,000
Amount due from related parties		0	0
Other assets (1)		8,000,000	0
Total assets		439,000,000	483,000,000
Short-term interest bearing debt		48,000,000	51,000,000
Long-term interest bearing debt		261,000,000	305,000,000
Other liabilities		0	1,000,000
Short-term debt due to related parties		4,000,000	0
Long-term debt due to related parties (2)	[3]	121,000,000	126,000,000
Total liabilities		434,000,000	483,000,000
Equity		5,000,000	0
Book value of units in the Company's consolidated accounts		515,000,000	537,000,000
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Cash and cash equivalents		17,000,000	0
Dividend to non-controlling interests in VIEs		14,000,000	113,000,000
Affiliated Entity | SFL Hercules Ltd
Variable Interest Entity [Line Items]
Amount due from related parties - current			59,000,000
Affiliated Entity | SFL Deepwater Limited
Variable Interest Entity [Line Items]
Amount due from related parties - current			$ 26,000,000
Amounts due to related parties - current		$ 0
[1]	Text selection found with no content.
[2]	The fixed assets referred to in the table above exclude assets under construction. Asset locations at the end of a period are not necessarily indicative of the geographic distribution of the revenues or operating profits generated by such assets during such period.
[3]	We present balances due to/from Ship Finance on a net basis, due to the fact that there is a right to offset established in the long-term loan agreements, and the balances are intended to be settled on a net basis. As at December 31, 2016, the balances offset were $26 million related to SFL Deepwater Ltd and $59 million related to SFL Hercules Ltd against "Long term debt due to related parties" within "Non-current liabilities" in the Consolidated Balance Sheet. As at December 31, 2017, we have no receivable balances presented against "Long term debt due to related parties" within "Non-current liabilities" in the Consolidated Balance Sheet.

Assets held for sale (Details)

Assets held for sale (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 05, 2018	Jun. 03, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment owned (as percent)						23.00%
Loss on disposal	[1]	$ (245,000,000)	$ 0	$ (63,000,000)
Disposal Group, Including Discontinued Operation, Assets, Noncurrent [Roll Forward]
Opening balance, Non-current assets held for sale		128,000,000
Loss on disposals	[1]	(245,000,000)	0	(63,000,000)
Closing balance, Non-current assets held for sale		126,000,000	128,000,000
Drilling units | Sale of West Rigel
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Fair value of consideration received		126,000,000
Loss on disposal		(2,000,000)
Disposal Group, Including Discontinued Operation, Assets, Noncurrent [Roll Forward]
Loss on disposals		(2,000,000)
Closing balance, Non-current assets held for sale		126,000,000
Jurong Shipyard
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment owned (as percent)						77.00%
Assets held for sale | Drilling units | Sale of West Rigel
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal		(2,000,000)	0
Disposal Group, Including Discontinued Operation, Assets, Noncurrent [Roll Forward]
Opening balance, Non-current assets held for sale		128,000,000	128,000,000
West Rigel newbuild investment, classified as held for sale		0	0
Loss on disposals		(2,000,000)	0
Closing balance, Non-current assets held for sale		$ 126,000,000	$ 128,000,000	$ 128,000,000
Subsequent Event | Jurong Shipyard | Drilling units | Sale of West Rigel
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Fair value of consideration received					$ 126,000,000
[1]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".

Supplementary cash flow info189

Supplementary cash flow information (Details) - USD ($)		Apr. 29, 2017	Dec. 05, 2016	Aug. 31, 2017	Jul. 31, 2017	Jun. 30, 2016	May 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015		Sep. 12, 2017	Jun. 29, 2016	Jun. 13, 2016	May 30, 2016	May 20, 2016	Dec. 31, 2012	Sep. 30, 2012	May 10, 2005
Schedule of Supplemental Cash Flow Elements [Line Items]
Disposal of subsidiaries - existing bank loan repaid	[1]							$ 0	$ 0	$ 150,000,000
Sale of rigs and equipment	[2]							103,000,000	0	0
Notional amount of investments acquired	[3]								(6,000,000)
Proceeds from repayment of short-term loan from related parties due to Seadrill Partners insulation from Seadrill Limited	[4]							109,000,000
Derecognition of Sevan Developer newbuild asset								620,000,000	0	0
Derecognition of Sevan Developer construction obligation								(526,000,000)	0	0
Repayment of bank loan through disposal of subsidiaries	[1]									(150,000,000)
Repayment of debt following sale of rigs and equipment	[2]							(103,000,000)
Repayment relating to share forward contracts and other derivatives	[5]									(136,000,000)
Repayment relating to SapuraKencana financing agreements								(754,000,000)	(1,054,000,000)	(2,999,000,000)	[6]
Conversion of convertible bond into shares, decrease in long term debt	[7]								(105,000,000)
Conversion of convertible bond into shares, net increase in equity	[7]								58,000,000
Increase in non-controlling interest in Seadrill Nigeria Operations Ltd	[3]								7,000,000
Proceeds from long-term loans	[8]							0	150,000,000	0
Long-term loans netted down with related party balances	[8]							0	(150,000,000)	0
Dividend to non-controlling interests in VIEs	[4]								(113,000,000)	0
Repayment of debt following insulation of Seadrill Partners from Seadrill Limited	[4]							(109,000,000)	0	0
Sale of rigs and equipment								$ 122,000,000	0	$ 0	[6]
Conversion of convertible bond									$ 58,000,000
Number of shares issued (in shares)									15,684,340
Common shares, par value (in dollars per share)						$ 2	$ 2	$ 2	$ 2										$ 2
Common stock, shares issued (in shares)								508,763,020	508,763,020	493,078,680				508,444,280		500,944,280			6,000
Common shares, shares outstanding (in shares)								504,518,940	504,444,280	492,759,940		508,763,020		508,444,280		500,944,280
Loss on disposals	[9]							$ 245,000,000	$ 0	$ 63,000,000
Variable Interest Entity, Primary Beneficiary
Schedule of Supplemental Cash Flow Elements [Line Items]
Dividend to non-controlling interests in VIEs	[4]							(14,000,000)
Convertible bonds due 2017
Schedule of Supplemental Cash Flow Elements [Line Items]
Number of shares issued due to conversion of convertible debt instruments (in shares)										0
$1,000 million fixed interest bond
Schedule of Supplemental Cash Flow Elements [Line Items]
Fixed interest rate (as percent)						6.125%	6.125%						5.625%		5.625%			5.625%
Number of shares issued (in shares)						7,500,000	8,184,340
Debt repurchased						$ 50,000,000	$ 55,000,000
SapuraKencana
Schedule of Supplemental Cash Flow Elements [Line Items]
Repayment relating to SapuraKencana financing agreements	[10]								$ (160,000,000)	$ (93,000,000)
Seadrill Mobile Units (Nigeria) Ltd
Schedule of Supplemental Cash Flow Elements [Line Items]
Ownership interest (as percent)			51.00%
Seadrill UK Ltd | Seadrill Mobile Units (Nigeria) Ltd
Schedule of Supplemental Cash Flow Elements [Line Items]
Notional amount of investments acquired			$ (6,600,000)
Interest acquired (as percent)			10.00%
Ownership interest (as percent)			49.00%
Drilling units | West Triton, West Mischief and West Resolute
Schedule of Supplemental Cash Flow Elements [Line Items]
Sale of rigs and equipment								122,000,000
Fair value of consideration received		$ 225,000,000
Loss on disposals		$ 166,000,000
Drilling units | Disposal of Sevan Developer contract
Schedule of Supplemental Cash Flow Elements [Line Items]
Fair value of consideration received								0
Disposal group, including discontinued operation, property, plant and equipment					$ 620,000,000
Disposal group, including discontinued operation, construction payable					526,000,000
Disposal group, including discontinued operation, accrued liabilities					19,000,000
Loss on disposals					75,000,000			75,000,000
$440 million facility | Secured Debt
Schedule of Supplemental Cash Flow Elements [Line Items]
Repayments of debt				$ 109,000,000
Principal amount					$ 440,000,000			$ 440,000,000									$ 440,000,000
[1]	During the year ended December 31, 2015, existing debt of ours was directly settled as consideration for the disposal of certain drilling rigs to the SeaMex joint venture - refer to Note 6 "(Loss)/gain on disposals" for further information.
[2]	During the year ended December 31, 2017, we completed our sale of the West Triton, West Resolute and West Mischief to Shelf Drilling , receiving cash consideration of $122 million. This comprised sales value of $225 million offset by $103 million of debt repayments. Refer to Note 6 "(Loss)/gain on disposals" for further information.
[3]	uring the year ended December 31, 2016, certain consolidated VIEs of ours withdrew bank loans and made loans to the related party Ship Finance International. These balances are presented net in the consolidated statement of cash flows. Refer to Note 22 "Long-term debt" for further information.
[4]	During the year ended December 31, 2017, the Ship Finance VIEs that we consolidate declared dividends payable totaling $14 million to Ship Finance (December 31, 2016: $113 million). Refer to Note 34 "Variable interest entities" for further information.9.In August 2017, Seadrill Partners amended certain credit facilities to insulate itself from Seadrill Limited. This resulted in a $109 million repayment in respect to the $440 million secured debt facility. Refer to Note 30 "Related party transactions" for further information on related party transactions.
[5]	During the year ended December 31, 2015, we settled Sevan share repurchase agreements using cash balances already classified as restricted.
[6]	Text selection found with no content.
[7]	In May 2016, we entered into a privately negotiated exchange agreement with certain holders of our outstanding 5.625%(subsequently increased to 6.125%) Senior Notes due in 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 8,184,340 new shares of our common stock, par value $2.00 per share, in exchange for $55 million principal amount of the 2017 Notes. Settlement occurred on May 20, 2016, upon which we had a total of 500,944,280 shares of our common stock issued and outstanding. In June 2016, we entered into another privately negotiated exchange agreement with certain holders of our outstanding 5.625% (subsequently increased to 6.125%) Senior Notes due 2017 (the "2017 Notes"), pursuant to which we agreed to issue a total of 7,500,000 new shares of our common stock, par value $2.00 per share, in exchange for $50 million principal amount of the 2017 Notes. We had a total of 508,444,280 shares of our common stock issued and outstanding, post settlement on June 13, 2016.
[8]	During the year ended December 31, 2017, the Ship Finance VIEs that we consolidate declared dividends payable totaling $14 million to Ship Finance (December 31, 2016: $113 million). Refer to Note 34 "Variable interest entities" for further information.
[9]	Includes transactions with related parties. Refer to Note 30 "Related party transactions".
[10]	During the years ended December 31, 2016 and December 31, 2015, we settled SapuraKencana financing agreements using cash balances already classified as restricted.

Subsequent Events - (Details)

Subsequent Events - (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	[1]	Apr. 05, 2018
Subsequent Event [Line Items]
Debtor reorganization items, claims settlement accrual	$ 1,064
Loss on impairment of long lived assets	696	$ 44	$ 563
West Dorado, West Draco, West Aquila and West Libra
Subsequent Event [Line Items]
Loss on impairment of long lived assets	696
Sale of West Rigel | Drilling units
Subsequent Event [Line Items]
Fair value of consideration received	$ 126
Sale of West Rigel | Subsequent Event | Drilling units | Jurong Shipyard
Subsequent Event [Line Items]
Fair value of consideration received					$ 126
[1]	Text selection found with no content.