Diamond Offshore Drilling (DODRW) 10-K 13 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 09, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	DO
Entity Registrant Name	DIAMOND OFFSHORE DRILLING, INC.
Entity Central Index Key	949,039
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		137,227,782
Entity Public Float			$ 694,258,330

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 376,037	$ 156,233
Accounts receivable, net of allowance for bad debts	256,730	247,028
Prepaid expenses and other current assets	157,625	102,146
Assets held for sale	96,261	400
Total current assets	886,653	505,807
Drilling and other property and equipment, net of accumulated depreciation	5,261,641	5,726,935
Other assets	102,276	139,135
Total assets	6,250,570	6,371,877
Current liabilities:
Accounts payable	38,755	30,242
Accrued liabilities	154,655	182,159
Taxes payable	29,878	23,898
Short-term borrowings	0	104,200
Total current liabilities	223,288	340,499
Long-term debt	1,972,225	1,980,884
Deferred tax liability	167,299	197,011
Other liabilities	113,497	103,349
Total liabilities	2,476,309	2,621,743
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock (par value $0.01, 25,000,000 shares authorized, none issued and outstanding)
Common stock (par value $0.01, 500,000,000 shares authorized; 144,085,292 shares issued and 137,227,782 shares outstanding at December 31, 2017; 143,997,757 shares issued and 137,169,663 shares outstanding at December 31, 2016)	1,441	1,440
Additional paid-in capital	2,011,397	2,004,514
Retained earnings	1,964,497	1,946,765
Accumulated other comprehensive gain (loss)	(5)	1
Treasury stock, at cost (6,857,510 and 6,828,094 shares of common stock at December 31, 2017 and 2016, respectively)	(203,069)	(202,586)
Total stockholders' equity	3,774,261	3,750,134
Total liabilities and stockholders' equity	$ 6,250,570	$ 6,371,877

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	144,085,292	143,997,757
Common stock, shares outstanding	137,227,782	137,169,663
Treasury stock, shares	6,857,510	6,828,094

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Contract drilling	$ 1,451,219	$ 1,525,214	$ 2,360,184
Revenues related to reimbursable expenses	34,527	75,128	59,209
Total revenues	1,485,746	1,600,342	2,419,393
Operating expenses:
Contract drilling, excluding depreciation	801,964	772,173	1,227,864
Reimbursable expenses	33,744	58,058	58,050
Depreciation	348,695	381,760	493,162
General and administrative	74,505	63,560	66,462
Impairment of assets	99,313	678,145	860,441
Bad debt recovery	0	(265)	0
Restructuring and separation costs	14,146		9,778
(Gain) loss on disposition of assets	(10,500)	3,795	(2,290)
Total operating expenses	1,361,867	1,957,226	2,713,467
Operating income (loss)	123,879	(356,884)	(294,074)
Other income (expense):
Interest income	2,473	768	3,322
Interest expense, net of amounts capitalized	(113,528)	(89,934)	(93,934)
Foreign currency transaction (loss) gain	(1,128)	(11,522)	2,465
Loss on extinguishment of senior notes	(35,366)
Other, net	2,230	(10,727)	873
Loss before income tax benefit	(21,440)	(468,299)	(381,348)
Income tax benefit	39,786	95,796	107,063
Net income (loss)	$ 18,346	$ (372,503)	$ (274,285)
Earnings (loss) per share:
Basic	$ 0.13	$ (2.72)	$ (2)
Diluted	$ 0.13	$ (2.72)	$ (2)
Weighted-average shares outstanding:
Shares of common stock	137,213	137,168	137,157
Dilutive potential shares of common stock	52
Total weighted-average shares outstanding	137,265	137,168	137,157

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income or Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 18,346	$ (372,503)	$ (274,285)
Derivative financial instruments:
Unrealized holding loss			(1,574)
Reclassification adjustment for (gain) loss included in net income (loss)	(6)	(5)	5,084
Investments in marketable securities:
Unrealized holding loss on investments		(6,559)	(4,940)
Reclassification adjustment for loss included in net income (loss)		11,600
Total other comprehensive (loss) gain	(6)	5,036	(1,430)
Comprehensive income (loss)	$ 18,340	$ (367,467)	$ (275,715)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Gains (Losses) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2014	$ 4,451,563	$ 1,440	$ 1,993,898	$ 2,661,999	$ (3,605)	$ (202,169)
Beginning Balance, shares at Dec. 31, 2014		143,960,260				6,812,361
Net income (loss)	(274,285)			(274,285)
Dividends to stockholders	(68,578)			(68,578)
Stock-based compensation, net of tax			5,736
Stock-based compensation, vested shares issued (withheld), shares		18,617				7,810
Stock-based compensation, vested shares issued (withheld), value						$ (236)
Stock-based compensation expense, net of shares withheld for taxes	5,500
Net gain (loss) on derivative financial instruments	3,510				3,510
Net gain (loss) on investments	(4,940)				(4,940)
Ending Balance at Dec. 31, 2015	4,112,770	$ 1,440	1,999,634	2,319,136	(5,035)	$ (202,405)
Ending Balance, shares at Dec. 31, 2015		143,978,877				6,820,171
Net income (loss)	(372,503)			(372,503)
Anti-dilution adjustment	132			132
Stock-based compensation, net of tax			4,880
Stock-based compensation, vested shares issued (withheld), shares		18,880				7,923
Stock-based compensation, vested shares issued (withheld), value						$ (181)
Stock-based compensation expense, net of shares withheld for taxes	4,699
Net gain (loss) on derivative financial instruments	(5)				(5)
Net gain (loss) on investments	5,041				5,041
Ending Balance at Dec. 31, 2016	3,750,134	$ 1,440	2,004,514	1,946,765	1	$ (202,586)
Ending Balance, shares at Dec. 31, 2016		143,997,757				6,828,094
Impact of change in accounting policy			634	(634)
Adjusted balance at December 31, 2016 at Dec. 31, 2017	3,750,134	$ 1,440	2,005,148	1,946,131	1	$ (202,586)
Adjusted balance at December 31, 2016, shares at Dec. 31, 2017		143,997,757				6,828,094
Net income (loss)	18,346			18,346
Anti-dilution adjustment	20			20
Stock-based compensation, net of tax		$ 1	6,249
Stock-based compensation, vested shares issued (withheld), shares		87,535				29,416
Stock-based compensation, vested shares issued (withheld), value						$ (483)
Stock-based compensation expense, net of shares withheld for taxes	5,767
Net gain (loss) on derivative financial instruments	(6)				(6)
Ending Balance at Dec. 31, 2017	$ 3,774,261	$ 1,441	$ 2,011,397	$ 1,964,497	$ (5)	$ (203,069)
Ending Balance, shares at Dec. 31, 2017		144,085,292				6,857,510

Consolidated Statements of Sto7

Consolidated Statements of Stockholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2015$ / shares
Retained Earnings [Member]
Stockholders dividends per share	$ 0.50

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income (loss)	$ 18,346	$ (372,503)	$ (274,285)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation	348,695	381,760	493,162
Loss on impairment of assets	99,313	678,145	860,441
Loss on extinguishment of senior notes	35,366
Restructuring and separation costs	14,146		9,778
(Gain) loss on disposition of assets	(10,500)	3,795	(2,290)
Loss on sale of marketable securities, net		12,146
Loss on foreign currency forward exchange contracts			8,364
Deferred tax provision	(72,127)	(106,263)	(242,034)
Stock-based compensation expense	6,250	4,880	4,856
Deferred income, net	8,676	(29,108)	(45,383)
Deferred expenses, net	46,337	(20,155)	(26,405)
Other assets, noncurrent	(326)	(4,914)	2,483
Other liabilities, noncurrent	(963)	(31)	(3,890)
Payments of settlement of foreign currency forward exchange contracts designated as accounting hedges			(8,364)
Other	7,708	5,691	858
Changes in operating assets and liabilities:
Accounts receivable	(11,049)	159,098	58,872
Prepaid expenses and other current assets	(1,291)	6,187	19,195
Accounts payable and accrued liabilities	19,803	(71,085)	(180,872)
Taxes payable	(14,576)	(1,089)	71,719
Net cash provided by operating activities	493,808	646,554	736,427
Investing activities:
Capital expenditures (including rig construction)	(139,581)	(652,673)	(830,655)
Proceeds from disposition of assets, net of disposal costs	15,196	221,722	13,049
Proceeds from sale and maturities of marketable securities	35	4,614	51
Net cash used in investing activities	(124,350)	(426,337)	(817,555)
Financing activities:
Repayment of long-term debt	(500,000)		(250,000)
Payment of debt extinguishment costs	(34,395)
Proceeds from issuance of senior notes	496,360
(Repayment of) proceeds from short-term borrowings, net	(104,200)	(182,389)	286,589
Debt issuance costs and arrangement fees	(7,263)	(215)	(624)
Payment of dividends and anti-dilution payments	(156)	(408)	(69,432)
Net cash used in financing activities	(149,654)	(183,012)	(33,467)
Net change in cash and cash equivalents	219,804	37,205	(114,595)
Cash and cash equivalents, beginning of year	156,233	119,028	233,623
Cash and cash equivalents, end of year	$ 376,037	$ 156,233	$ 119,028

General Information

General Information	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
General Information	1. General Information Diamond Offshore Drilling, Inc. provides contract drilling services to the energy industry around the globe with a fleet of 17 offshore drilling rigs, consisting of four drillships and seven ultra-deepwater, four deepwater and two mid-water Ocean Victory jack-up Ocean Scepter, Ocean Victory As of February 9, 2018, Loews Corporation, or Loews, owned approximately 53% of the outstanding shares of our common stock. Principles of Consolidation Our consolidated financial statements include the accounts of Diamond Offshore Drilling, Inc. and our wholly-owned subsidiaries after elimination of intercompany transactions and balances. Use of Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with accounting principles generally accepted in the United States, or U.S., or GAAP, 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 amount of revenues and expenses during the reporting period. Actual results could differ from those estimated. Cash and Cash Equivalents We consider short-term, highly liquid investments that have an original maturity of three months or less and deposits in money market mutual funds that are readily convertible into cash to be cash equivalents. The effect of exchange rate changes on cash balances held in foreign currencies was not material for the years ended December 31, 2017, 2016 and 2015. Provision for Bad Debts We record a provision for bad debts on a case-by-case Assets Held For Sale We reported the $96.3 million and $0.4 million carrying values of certain of our rigs being marketed for sale as “Assets held for sale” in our Consolidated Balance Sheets at December 31, 2017 and 2016, respectively. The Ocean Victory Ocean Scepter jack-up Ocean Spur Drilling and Other Property and Equipment We carry our drilling and other property and equipment at cost, less accumulated depreciation. Maintenance and routine repairs are charged to income currently while replacements and betterments that upgrade or increase the functionality of our existing equipment and that significantly extend the useful life of an existing asset are capitalized. Significant judgments, assumptions and estimates may be required in determining whether or not such replacements and betterments meet the criteria for capitalization and in determining useful lives and salvage values of such assets. Changes in these judgments, assumptions and estimates could produce results that differ from those reported. During the years ended December 31, 2017 and 2016, we capitalized $69.4 million and $177.6 million, respectively, in replacements and betterments of our drilling fleet. Costs incurred for major rig upgrades and/or the construction of rigs are accumulated in construction work-in-progress, Capitalized Interest We capitalize interest cost for rig construction or upgrades, as well as other qualifying projects. During the three years ended December 31, 2017, we capitalized interest on qualifying expenditures, primarily related to our rig construction projects. A reconciliation of our total interest cost to “Interest expense, net of amounts capitalized” as reported in our Consolidated Statements of Operations is as follows: For the Year Ended December 31, 2017 2016 2015 (In thousands) Total interest cost including amortization of debt issuance costs $ 113,618 $ 110,748 $ 110,242 Capitalized interest (90 ) (20,814 ) (16,308 ) Total interest expense as reported $ 113,528 $ 89,934 $ 93,934 Impairment of Long-Lived Assets We evaluate our property and equipment for impairment whenever changes in circumstances indicate that the carrying amount of an asset may not be recoverable (such as, but not limited to, cold stacking a rig, the expectation of cold stacking a rig in the near term, contracted backlog of less than one year for a rig, a decision to retire or scrap a rig, or excess spending over budget on a newbuild, construction project or major rig upgrade). We utilize an undiscounted probability-weighted cash flow analysis in testing an asset for potential impairment. Our assumptions and estimates underlying this analysis include the following: • dayrate by rig; • utilization rate by rig if active, warm stacked or cold stacked (expressed as the actual percentage of time per year that the rig would be used at certain dayrates); • the per day operating cost for each rig if active, warm stacked or cold stacked; • the estimated annual cost for rig replacements and/or enhancement programs; • the estimated maintenance, inspection or other reactivation costs associated with a rig returning to work; • salvage value for each rig; and • estimated proceeds that may be received on disposition of each rig. Based on these assumptions, we develop a matrix for each rig under evaluation using multiple utilization/dayrate scenarios, to each of which we have assigned a probability of occurrence. We arrive at a projected probability-weighted cash flow for each rig based on the respective matrix and compare such amount to the carrying value of the asset to assess recoverability. The underlying assumptions and assigned probabilities of occurrence for utilization and dayrate scenarios are 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, inspection and reactivation costs, are estimated using historical data adjusted for known developments, cost projections for re-entry Management’s assumptions are necessarily subjective and are an inherent part of our asset impairment evaluation , oil-producing Fair Value of Financial Instruments We believe that the carrying amount of our current financial instruments approximates fair value because of the short maturity of these instruments. See Note 7. Debt Issuance Costs Deferred costs associated with our senior notes are presented in our Consolidated Balance Sheets at December 31, 2017 and 2016 as a reduction in the related long-term debt and are amortized over the respective terms of the related debt. See Note 9. Income Taxes We account for income taxes in accordance with accounting standards that require the recognition of the amount of taxes payable or refundable for the current year and an asset and liability approach in recognizing the amount of deferred tax liabilities and assets for the future tax consequences of events that have been currently recognized in our financial statements or tax returns. In each of our tax jurisdictions we recognize a current tax liability or asset for the estimated taxes payable or refundable on tax returns for the current year and a deferred tax asset or liability for the estimated future tax effects attributable to temporary differences and carryforwards. Deferred tax assets are reduced by a valuation allowance, if necessary, which is determined by the amount of any tax benefits that, based on available evidence, are not expected to be realized under a “more likely than not” approach. Deferred tax assets and liabilities are classified as noncurrent in a classified statement of financial position. We make judgments regarding future events and related estimates especially as they pertain to the forecasting of our effective tax rate, the potential realization of deferred tax assets such as utilization of foreign tax credits, and exposure to the disallowance of items deducted on tax returns upon audit. We record interest related to accrued unrecognized tax positions in “Interest expense, net of amounts capitalized” and recognize penalties associated with uncertain tax positions in “Income tax benefit” in our Consolidated Statements of Operations. Liabilities for uncertain tax positions, including any penalty, are denominated in the currency of the related tax jurisdiction and are revalued for changes in currency exchange rates. The revaluation of such liabilities for uncertain tax positions is reported in “Income tax benefit” in our Consolidated Statements of Operations. See Note 15. Treasury Stock In connection with the vesting of restricted stock units held by certain individuals, we acquired 29,416 and 7,923 shares of our common stock during 2017 and 2016, respectively (valued at $0.5 million in 2017 and $0.2 million in 2016), in satisfaction of tax withholding obligations that were incurred on the vesting date. See Note 4. Depending on market conditions, we may, from time to time, purchase shares of our common stock in the open market or otherwise. We account for the purchase of treasury stock using the cost method, which reports the cost of the shares acquired in “Treasury stock” as a deduction from stockholders’ equity in our Consolidated Balance Sheets. We did not repurchase any shares of our outstanding common stock during 2017, 2016 or 2015. Comprehensive Income (Loss) Comprehensive income (loss) is the change in equity of a business enterprise during a period from transactions and other events and circumstances except those transactions resulting from investments by owners and distributions to owners. Comprehensive income (loss) for the three years ended December 31, 2017, 2016 and 2015 includes net income (loss) and unrealized holding gains and losses on marketable securities and financial derivatives designated as cash flow accounting hedges. See Note 10. Foreign Currency Our functional currency is the U.S. dollar. Transactions incurred in currencies other than the U.S. dollar are subject to gains or losses due to fluctuations in those currencies. We report foreign currency transaction gains and losses as “Foreign currency transaction (loss) gain” in our Consolidated Statements of Operations and may also include, when applicable, unrealized gains and losses to record the carrying value of foreign currency forward exchange, or FOREX, contracts not designated as accounting hedges and realized gains and losses from the settlement of such contracts. The revaluation of assets and liabilities related to foreign income taxes, including deferred tax assets and liabilities and uncertain tax positions, including any penalty, is reported in “Income tax benefit (expense)” in our Consolidated Statements of Operations. Revenue Recognition We recognize revenue from dayrate drilling contracts as services are performed. In connection with such drilling contracts, we may receive fees (on either a lump-sum Some of our drilling contracts require downtime before the start of the contract to prepare the rig to meet customer requirements. At times, we may be compensated by the customer for such work (on either a lump-sum From time to time, we may receive fees from our customers for capital improvements to our rigs (on either a lump-sum We record reimbursements received for the purchase of supplies, equipment, personnel services and other services provided at the request of our customers in accordance with a contract or agreement, for the gross amount billed to the customer, as “Revenues related to reimbursable expenses” in our Consolidated Statements of Operations. Recent Accounting Pronouncements In October 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory, 2016-16. 2016-16 2016-16. 2016-16 In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments 2016-15. 2016-15 zero-coupon 2016-15 2016-15 2016-15 In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) 2016-02, non-lease 2016-02, 2016-02 Non-lease 2014-09. 2016-02 2016-02 2016-02 2016-02, In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09, 2014-09 2014-09 2014-09

Asset Impairments

Asset Impairments	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Asset Impairments	2. Asset Impairments 2017 Impairments. jack-up We estimated the fair value of two of the 2017 Impaired Rigs using an income approach in which the fair value was estimated based on a calculation of the rig’s discounted future net cash flows over its remaining economic life, which utilized significant unobservable inputs, including, but not limited to, assumptions related to estimated dayrate revenue, rig utilization, estimated reactivation and regulatory survey costs, as well as estimated proceeds that may be received on ultimate disposition of the rig. The fair value of the other 2017 Impaired Rig was estimated using a market approach, which required us to estimate the value that would be received for the rig in the principal or most advantageous market for that rig in an orderly transaction between market participants. This estimate was primarily based on an indicative bid to purchase the rig, as well as our evaluation of other market data points; however, the rig has not been sold. Our fair value estimates were representative of Level 3 fair value measurements due to the significant level of estimation involved and the lack of transparency as to the inputs used. During the second and fourth quarters of 2017, we recorded impairment losses of $71.3 million and $28.0 million, respectively, or an aggregate impairment loss of $99.3 million for the year ended December 31, 2017 related to our 2017 Impaired Rigs. 2016 Impairments. mid-water We estimated the fair value of the 2016 Impaired Rigs using an income approach, as described above. Our fair value estimates were representative of Level 3 fair value measurements due to the significant level of estimation involved and the lack of transparency as to the inputs used. During the second quarter of 2016, we recorded an impairment loss of $670.0 million related to our 2016 Impaired Rigs. 2015 Impairments mid-water jack-up We estimated the fair value of 16 of the 2015 Impaired Rigs utilizing a market approach, as described above. We estimated the fair value of the one remaining 2015 Impaired Rig using an income approach, as discussed above. Our fair value estimates are representative of Level 3 fair value measurements due to the significant level of estimation involved and the lack of transparency as to the inputs used. During the first, third and fourth quarters of 2015, we recognized impairment losses of $358.5 million, $2.6 million and $499.4 million, respectively, for an aggregate impairment loss of $860.4 million for the year ended December 31, 2015. See Notes 1 and 8.

Supplemental Financial Informat

Supplemental Financial Information	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Financial Information	3. Supplemental Financial Information Consolidated Balance Sheet Information Accounts receivable, net of allowance for bad debts, consists of the following: December 31, 2017 2016 (In thousands) Trade receivables $ 247,453 $ 236,040 Value added tax receivables 14,067 14,639 Related party receivables 205 149 Other 464 1,659 262,189 252,487 Allowance for bad debts (5,459 ) (5,459 ) Total $ 256,730 $ 247,028 An analysis of the changes in our provision for bad debts for each of the three years ended December 31, 2017, 2016 and 2015 is as follows: For the Year Ended December 31, 2017 2016 2015 (In thousands) Allowance for bad debts, beginning of year $ 5,459 $ 5,724 $ 5,724 Bad debt recovery — (265 ) — Allowance for bad debts, end of year $ 5,459 $ 5,459 $ 5,724 See Note 7 for a discussion of our provision for bad debts and write off of uncollectible accounts against the reserve. Prepaid expenses and other current assets consist of the following: December 31, 2017 2016 (In thousands) Rig spare parts and supplies $ 28,383 $ 25,343 Deferred mobilization costs 51,297 61,488 Prepaid BOP Lease 3,873 3,873 Prepaid insurance 3,091 3,771 Prepaid taxes 67,212 2,894 Other 3,769 4,777 Total $ 157,625 $ 102,146 During 2016, we recognized an $8.1 million impairment loss related to our rig spare parts and supplies. Accrued liabilities consist of the following: December 31, 2017 2016 (In thousands) Rig operating expenses $ 48,894 $ 33,732 Payroll and benefits 46,560 45,619 Deferred revenue 11,371 9,522 Accrued capital project/upgrade costs 3,698 60,308 Interest payable 28,234 18,365 Personal injury and other claims 5,699 6,424 Other 10,199 8,189 Total $ 154,655 $ 182,159 “Accrued liabilities” at December 31, 2017, includes $13.6 million in accrued costs related to our 2017 Reduction Plan of which $11.5 million and $2.1 million were reported as “Rig operating expenses” and “Payroll and benefits,” respectively. See Note 14. Consolidated Statement of Cash Flows Information Noncash investing activities excluded from the Consolidated Statements of Cash Flows and other supplemental cash flow information is as follows: December 31, 2017 2016 2015 (In thousands) Accrued but unpaid capital expenditures at period end $ 3,698 $ 60,308 $ 84,146 Common stock withheld for payroll tax obligations (1) 483 181 236 Cash interest payments (2) 97,096 105,987 110,412 Cash income taxes paid (refunded), net: U.S. federal — (31,151 ) (21,751 ) Foreign 43,999 48,931 69,697 State 94 1 58 (1) Represents the cost of 29,416 and 7,923 shares of common stock withheld to satisfy the payroll tax obligation incurred as a result of the vesting of restricted stock units in 2017 and 2016, respectively. These costs are presented as a deduction from stockholders’ equity in “Treasury stock” in our Consolidated Balance Sheets at December 31, 2017 and 2016. (2) Interest payments, net of amounts capitalized, were $97.0 million, $86.1 million and $94.7 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	4. Stock-Based Compensation We have an Equity Incentive Compensation Plan, or Equity Plan, for our officers, independent contractors, employees and non-employee • Stock options (including incentive stock options and nonqualified stock options); • Stock appreciation rights, or SARs; • Restricted stock; • Restricted stock units, or RSUs; • Performance shares or units; and • Other stock-based awards (including dividend equivalents). A maximum of 7,500,000 shares of our common stock is available for the grant or settlement of awards under the Equity Plan, subject to adjustment for certain business transactions and changes in capital structure. Vesting conditions and other terms and conditions of awards under the Equity Plan are determined by our Board of Directors or the compensation committee of our Board of Directors, subject to the terms of the Equity Plan. RSUs may be issued with performance-vesting or time-vesting features. Except for RSUs issued to our CEO, RSUs are not participating securities, and the holders of such awards have no right to receive regular dividends if or when declared. In March 2016, the FASB issued ASU No. 2016-09, Compensation — Stock Compensation (Topic 718) 2016-09. 2016-09 2016-09 2016-09 Retained Additional Paid-in Capital (In thousands) Balance as of January 1, 2017 before adoption $ 1,946,765 $ 2,004,514 Adjustment for making election to account for forfeitures as they occur (634 ) 634 Balance as of January 1, 2017 after adoption $ 1,946,131 $ 2,005,148 All other requirements of ASU 2016-09, Total compensation cost recognized for all awards under the Equity Plan (or its predecessor) for the years ended December 31, 2017, 2016 and 2015 was $8.7 million, $7.0 million and $5.7 million, respectively. Tax benefits recognized for the years ended December 31, 2017, 2016 and 2015 related thereto were $2.6 million, $2.4 million and $1.9 million, respectively. As of December 31, 2017 there was $11.2 million of total unrecognized compensation cost related to non-vested Time-Vesting Awards SARs The fair value of SARs granted under the Equity Plan (or its predecessor) during each of the years ended December 31, 2017, 2016 and 2015 was estimated using the Black Scholes pricing model with the following weighted average assumptions: Year Ended December 31, 2017 2016 2015 Expected life of SARs (in years) 7 7 6 Expected volatility 31.70 % 45.79 % 55.12 % Dividend yield — .60 % (1) 1.70 % Risk free interest rate 2.09 % 1.46 % 1.66 % (1) Represents dividend yield related to January 2016 grant of SARs prior to our decision in early 2016 to discontinue paying dividends. The expected life of SARs is based on historical data as is the expected volatility. The dividend yield is based on the current approved regular dividend rate in effect and the current market price at the time of grant. Risk free interest rates are determined using the U.S. Treasury yield curve at time of grant with a term equal to the expected life of the SARs. A summary of SARs activity under the Equity Plan as of December 31, 2017 and changes during the year then ended is as follows: Number of Weighted- Weighted- (Years) Aggregate Intrinsic (In Thousands) Awards outstanding at January 1, 2017 1,449,706 $ 67.43 Granted 66,000 $ 14.95 Exercised — Forfeited 5,240 $ 41.88 Expired 248,352 $ 90.95 Awards outstanding at December 31, 2017 1,262,114 $ 60.16 4.3 $ 272 Awards exercisable at December 31, 2017 1,230,382 $ 60.63 4.2 $ 272 The weighted-average grant date fair values per share of awards granted during the years ended December 31, 2017, 2016 and 2015 were $5.61, $9.32 and $14.44, respectively. The total intrinsic value of awards exercised during the years ended December 31, 2017, 2016 and 2015 was $0, $0 and $0, respectively. The total fair value of awards vested during the years ended December 31, 2017, 2016 and 2015 was $1.2 million, $2.2 million and $3.6 million, respectively. Restricted Stock Units One-half non-participating non-participative non-participating A summary of activity for time-vesting RSUs under the Equity Plan as of December 31, 2017 and changes during the year then ended is as follows: Number of Weighted- Nonvested awards at January 1, 2017 319,560 $ 23.13 Granted 276,085 $ 16.37 Vested 68,659 $ 25.08 Forfeited 55,697 $ 20.76 Nonvested awards at December 31, 2017 471,289 $ 19.15 The total fair value of time-vesting RSUs vested during the year ended December 31, 2017 was $1.1 million. No time-vesting RSUs vested during the years ended December 31, 2016 or 2015. Performance-Vesting Awards Restricted Stock Units non-participating, non-participative A summary of activity for performance-vesting RSUs under the Equity Plan as of December 31, 2017 and changes during the year then ended is as follows: Number of Weighted- Nonvested awards at January 1, 2017 431,706 $ 24.55 Granted 370,616 $ 16.61 Vested 18,876 $ 46.64 Forfeited 55,590 $ 19.95 Nonvested awards at December 31, 2017 727,856 $ 20.28 The total grant date fair value of the performance-vesting RSUs that vested during the years ended December 31, 2017, 2016 and 2015 was $0.3 million, $0.4 million and $0.6 million, respectively.

Earnings (Loss) Per Share

Earnings (Loss) Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	5. Earnings (Loss) Per Share A reconciliation of the numerators and the denominators of the basic and diluted per-share Year Ended December 31, 2017 2016 2015 (In thousands, except per share data) Net income (loss) — basic and diluted (numerator): $ 18,346 $ (372,503 ) $ (274,285 ) Weighted-average shares — basic (denominator): 137,213 137,168 137,157 Dilutive effect of stock-based awards 52 — — Weighted-average shares including conversions — diluted (denominator): 137,265 137,168 137,157 Earnings (loss) per share: Basic $ 0.13 $ (2.72 ) $ (2.00 ) Diluted $ 0.13 $ (2.72 ) $ (2.00 ) The following table sets forth the share effects of stock-based awards excluded from the computation of earnings (loss) per share, as the inclusion of such potentially dilutive shares would have been antidilutive for the periods presented. Year Ended December 31, 2017 2016 2015 (In thousands) Employee and director: Stock options — 7 26 SARs 1,315 1,505 1,553 RSUs 757 704 278

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	6. Derivative Financial Instruments Foreign Currency Forward Exchange Contracts Our international operations expose us to foreign exchange risk associated with our costs payable in foreign currencies. To manage this risk, in prior years we entered into FOREX contracts for future delivery of Australian dollars, Brazilian reais, British pounds sterling, Mexican pesos and Norwegian kroner. These forward contracts were derivatives as defined by GAAP. During the year ended December 31, 2015, we settled FOREX contracts with aggregate a notional value of approximately $91.6 million of which the entire aggregate amount was designated as an accounting hedge. During the year ended December 31, 2015 we did not enter into or settle any FOREX contracts that were not designated as accounting hedges. We did not enter into any FOREX contracts during 2017 or 2016 and there were no FOREX contracts outstanding at December 31, 2017 or 2016. During the year ended December 31, 2015, we recognized an aggregate loss of $8.4 million related to our FOREX contracts designated as hedging instruments, which was reported in Contract drilling expense in our Consolidated Statements of Operations. The following table presents the amounts recognized in our Consolidated Balance Sheets and Consolidated Statements of Operations related to our derivative financial instruments designated as cash flow hedges for the year ended December 31, 2015. For the Year Ended 2015 (In thousands) FOREX contracts: Amount of loss recognized in AOCGL on derivative (effective portion) $ (2,420) Location of loss reclassified from AOCGL into income (effective portion) Contract drilling, Amount of loss reclassified from AOCGL into income (effective portion) $ (7,829) Location of loss recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing) Foreign currency Amount of loss recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing) $ (1) During the year ended December 31, 2015, we did not reclassify any amounts from AOCGL due to the probability of an underlying forecasted transaction not occurring.

Financial Instruments and Fair

Financial Instruments and Fair Value Disclosures	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Value Disclosures	7. Financial Instruments and Fair Value Disclosures Concentrations of Credit and Market Risk Financial instruments that potentially subject us to significant concentrations of credit or market risk consist primarily of periodic temporary investments of excess cash, trade accounts receivable and investments in debt securities, including mortgage-backed securities. We generally place our excess cash investments in U.S. government backed short-term money market instruments through several financial institutions. At times, such investments may be in excess of the insurable limit. We periodically evaluate the relative credit standing of these financial institutions as part of our investment strategy. Concentrations of credit risk with respect to our trade accounts receivable are limited primarily due to the entities comprising our customer base. Since the market for our services is the offshore oil and gas industry, this customer base consists primarily of major and independent oil and gas companies and government-owned oil companies. Based on our current customer base and the geographic areas in which we operate, as well as the number of rigs currently working in a geographic area, we do not believe that we have any significant concentrations of credit risk at December 31, 2017. In general, before working for a customer with whom we have not had a prior business relationship and/or whose financial stability may be uncertain to us, we perform a credit review on that company. Based on that analysis, we may require that the customer present a letter of credit, prepay or provide other credit enhancements. We record a provision for bad debts on a case-by-case In December 2013, we entered into a settlement with Niko with respect to certain obligations under dayrate contracts for the Ocean Monarch Ocean Lexington Fair Values Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy prescribed by GAAP requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. There are three levels of inputs that may be used to measure fair value: Level 1 Quoted prices for identical instruments in active markets. Level 1 assets include short-term investments such as money market funds, U.S. Treasury Bills and Treasury notes. Our Level 1 assets at December 31, 2017 consisted of cash held in money market funds of $337.1 million and time deposits of $20.9 million. Our Level 1 assets at December 31, 2016 consisted of cash held in money market funds of $125.7 million and time deposits of $20.6 million. Level 2 Quoted market prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. Level 2 assets and liabilities may include residential mortgage-backed securities, corporate bonds purchased in a private placement offering and over-the-counter Level 3 Valuations derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable. Level 3 assets and liabilities generally include financial instruments whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation or for which there is a lack of transparency as to the inputs used. Our Level 3 assets at December 31, 2017 and 2016 consisted of nonrecurring measurements of certain of our drilling rigs and associated spare parts and supplies for which we recorded an impairment loss during the second and fourth quarters of 2017 and the second quarter of 2016. See Notes 1, 2 and 3. Market conditions could cause an instrument to be reclassified among Levels 1, 2 and 3. Our policy regarding fair value measurements of financial instruments transferred into and out of levels is to reflect the transfers as having occurred at the beginning of the reporting period. There were no transfers between fair value levels during the years ended December 31, 2017 and 2016. Certain of our assets and liabilities are required to be measured at fair value on a recurring basis in accordance with GAAP. In addition, certain assets and liabilities may be recorded at fair value on a nonrecurring basis. Generally, we record assets at fair value on a nonrecurring basis as a result of impairment charges. We recorded impairment charges related to certain of our drilling rigs and related spare parts and supplies, which were measured at fair value on a nonrecurring basis in 2017 and 2016, respectively, and have presented the aggregate loss in “Impairment of assets” in our Consolidated Statements of Operations for the years ended December 31, 2017 and 2016. Assets and liabilities measured at fair value are summarized below. December 31, 2017 Fair Value Measurements Using Assets at Fair Total Losses for Year Ended (1) Level 1 Level 2 Level 3 (In thousands) Recurring fair value measurements: Assets: Short-term investments $ 358,019 $ — $ — $ 358,019 Nonrecurring fair value measurements: Assets: Impaired assets (2) $ — $ — $ 97,261 $ 97,261 $ 99,313 (1) Represents impairment losses of $71.3 million and $28.0 million recognized during the second and fourth quarters of 2017, respectively, related to our 2017 Impaired Rigs. See Note 2. (2) Represents the total book value as of December 31, 2017 of one ultra-deepwater rig and one deepwater semisubmersible rig, which were written down to their estimated fair value during the second quarter of 2017, and one jack-up December 31, 2016 Fair Value Measurements Using Assets at Fair Total Losses for Year Ended (1) Level 1 Level 2 Level 3 (In thousands) Recurring fair value measurements: Assets: Short-term investments $ 146,360 $ — $ — $ 146,360 Mortgage-backed securities — 35 — 35 Total assets $ 146,360 $ 35 $ — $ 146,395 Nonrecurring fair value measurements: Assets: Impaired assets (2) $ — $ — $ 69,153 $ 69,153 $ 678,145 (1) Represents impairment losses of $8.1 million and $670.0 million recognized during the year ended December 31, 2016 related to our rig spare parts and supplies and 2016 Impaired Rigs, respectively. See Notes 2 and 3. (2) Represents the total book value as of December 31, 2016 for 11 drilling rigs ($45.5 million) and for rig spare parts and supplies ($23.6 million), which were previously written down to their estimated fair value. Of the total fair value, $23.6 million, $0.4 million and $45.1 million were reported as “Prepaid expenses and other current assets,” “Assets held for sale” and “Drilling and other property and equipment, net of accumulated depreciation,” respectively, in our Consolidated Balance Sheets at December 31, 2016. See Notes 1, 2 and 3. We believe that the carrying amounts of our other financial assets and liabilities (excluding long-term debt), which are not measured at fair value in our Consolidated Balance Sheets, approximate fair value based on the following assumptions: • Cash and cash equivalents • Accounts receivable and accounts payable • Short-term borrowings We consider our senior notes, including current maturities, to be Level 2 liabilities under the GAAP fair value hierarchy and, accordingly, the fair value of our senior notes was derived using a third-party pricing service at December 31, 2017 and 2016. We perform control procedures over information we obtain from pricing services and brokers to test whether prices received represent a reasonable estimate of fair value. These procedures include the review of pricing service or broker pricing methodologies and comparing fair value estimates to actual trade activity executed in the market for these instruments occurring generally within a 10-day December 31, 2017 December 31, 2016 Fair Value Carrying Value Fair Value Carrying Value (In millions) 5.875% Senior Notes due 2019 $ — $ — $ 518.6 $ 499.8 3.45% Senior Notes due 2023 223.1 249.4 215.0 249.3 7.875% Senior Notes due 2025 523.1 496.5 — — 5.70% Senior Notes due 2039 405.0 497.2 392.5 497.1 4.875% Senior Notes due 2043 547.5 748.9 532.7 748.9 We have estimated the fair value amounts by using appropriate valuation methodologies and information available to management. Considerable judgment is required in developing these estimates, and accordingly, no assurance can be given that the estimated values are indicative of the amounts that would be realized in a free market exchange.

Drilling and Other Property and

Drilling and Other Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Drilling and Other Property and Equipment	8. Drilling and Other Property and Equipment Cost and accumulated depreciation of drilling and other property and equipment are summarized as follows: December 31, 2017 2016 (In thousands) Drilling rigs and equipment $ 7,971,406 $ 8,950,385 Land and buildings 63,309 64,449 Office equipment and other 82,691 73,108 Cost 8,177,406 9,087,942 Less accumulated depreciation (2,855,765 ) (3,361,007 ) Drilling and other property and equipment, net $ 5,261,641 $ 5,726,935 During the years ended December 31, 2017 and 2016, we recognized impairment losses of $99.3 million and $670.0 million, respectively. See Note 2.

Credit Agreement and Senior Not

Credit Agreement and Senior Notes	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Credit Agreement and Senior Notes	9. Credit Agreement and Senior Notes Credit Agreement We have a syndicated revolving credit agreement with Wells Fargo Bank, National Association, as administrative agent and swingline lender, that provides for a $1.5 billion senior unsecured revolving credit facility for general corporate purposes, which we refer to as the Credit Agreement. Our Credit Agreement matures on October 22, 2020, except for $40 million of commitments that mature on March 17, 2019 and $60 million of commitments that mature on October 22, 2019. In addition, we also have the option to increase the revolving commitments under the Credit Agreement by up to an additional $500 million from time to time, upon receipt of additional commitments from new or existing lenders, and to request one additional one-year Revolving loans under the Credit Agreement bear interest, at our option, at a rate per annum based on either an alternate base rate, or ABR, or a Eurodollar Rate, as defined in the Credit Agreement, plus the applicable interest margin for an ABR loan or a Eurodollar loan. Based on our current credit ratings, the applicable interest rate for ABR loans under the Credit Agreement is 0.25% over the greater of (i) the prime rate, (ii) the federal funds rate plus 0.50% and (iii) the daily one-month Swingline loans bear interest, at our option, at a rate per annum equal to (i) the ABR plus the applicable interest margin for ABR loans or (ii) the daily one-month Under the Credit Agreement, we also pay, based on our current long-term credit ratings, and as applicable, other customary fees including, but not limited to, a commitment fee on the unused commitments under the Credit Agreement of 0.20% per annum and a fronting fee to the issuing bank for each letter of credit. Participation fees for letters of credit are dependent upon the type of letter of credit issued, currently 0.625% per annum for performance letters of credit and 1.25% per annum for all other letters of credit. Favorable changes in our current credit ratings could lower the fees that we pay under the Credit Agreement; however, current interest rates and fees will apply should there be any further downgrade in our credit ratings. The Credit Agreement contains customary covenants, including, but not limited to, maintenance of a ratio of consolidated indebtedness to total capitalization, as defined in the Credit Agreement, of not more than 60% at the end of each fiscal quarter, as well as limitations on liens; mergers, consolidations, liquidation and dissolution; changes in lines of business; swap agreements; transactions with affiliates; and subsidiary indebtedness. As of December 31, 2017, we were in compliance with all covenant requirements. At December 31, 2017, we had no borrowings outstanding under the Credit Agreement. At February 9, 2018, we had no borrowings outstanding under the Credit Agreement and an additional $1.5 billion available. At December 31, 2016, we had $104.2 million in borrowings outstanding under the Credit Agreement that bore interest at a weighted average interest rate of 1.9%. Senior Notes At December 31, 2017, our senior notes were comprised of the following debt issues: Principal Amount Interest Rate Semiannual Interest Payment Dates Debt Issue (In millions) Maturity Date Coupon Effective 3.45% Senior Notes due 2023 $ 250.0 November 1, 2023 3.45% 3.50% May 1 and November 1 7.875% Senior Notes due 2025 $ 500.0 August 15, 2025 7.875% 8.00% February 15 and August 15 5.70% Senior Notes due 2039 $ 500.0 October 15, 2039 5.70% 5.75% April 15 and October 15 4.875% Senior Notes due 2043 $ 750.0 November 1, 2043 4.875% 4.89% May 1 and November 1 At December 31, 2017 and 2016, the carrying value of our senior notes, net of unamortized discount and debt issuance costs, was as follows: December 31, 2017 2016 (In thousands) 5.875% Senior Notes due 2019 $ — $ 498,679 3.45% Senior Notes due 2023 248,162 247,879 7.875% Senior Notes due 2025 489,420 — 5.70% Senior Notes due 2039 492,971 492,812 4.875% Senior Notes due 2043 741,672 741,514 Total senior notes, net $ 1,972,225 $ 1,980,884 As of December 31, 2017, the aggregate annual maturity of our senior notes, excluding net unamortized discounts and debt issuance costs of $8.1 million and $19.7 million, respectively, was as follows: Aggregate (In thousands) Year Ending December 31, 2018 $ — 2019 — 2020 — 2021 — 2022 — Thereafter 2,000,000 Total maturities of senior notes $ 2,000,000 Senior Notes Due 2019 Senior Notes Due 2025 The 2025 Notes are unsecured obligations of Diamond Offshore Drilling, Inc., and rank equally in right of payment to all of its existing and future senior indebtedness, and are structurally subordinated to all existing and future obligations of our subsidiaries. We have the right to redeem some or all of the 2025 Notes at any time or from time to time, on at least 15 days but not more than 60 days prior written notice, at the applicable redemption price specified in the governing indenture, plus accrued and unpaid interest to, but excluding, the date of redemption. The 2025 Notes contain customary covenants including limitations on liens, mergers, consolidations and certain sales of assets and on entering into sale and lease-back transactions covering a drilling rig or drillship, as specified in the governing indenture. Senior Notes Due 2023 and 2043 Senior Notes Due 2039

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Other Comprehensive Income (Loss)	10. Other Comprehensive Income (Loss) The following table sets forth the components of “Other comprehensive gain (loss)” and the related income tax effects thereon for the three years ended December 31, 2017 and the cumulative balances in AOCGL by component at December 31, 2017, 2016 and 2015. Unrealized Gain (Loss) on Total AOCGL Derivative Marketable (In thousands) Balance at January 1, 2015 (3,504 ) (101 ) (3,605 ) Change in other comprehensive loss before reclassifications, after tax of $846 and $(1) (1,574 ) (4,940 ) (6,514 ) Reclassification adjustments for items included in Net Loss, after tax of $(2,737) and $0 5,084 — 5,084 Total other comprehensive income (loss) 3,510 (4,940 ) (1,430 ) Balance at December 31, 2015 6 (5,041 ) (5,035 ) Change in other comprehensive loss before reclassifications, after tax of $0 and $2 — (6,559 ) (6,559 ) Reclassification adjustments for items included in Net Loss, after tax of $3 and $0 (5 ) 11,600 11,595 Total other comprehensive (loss) income (5 ) 5,041 5,036 Balance at December 31, 2016 1 — 1 Reclassification adjustments for items included in Net Loss, after tax of $2 and $0 (6 ) — (6 ) Total other comprehensive loss (6 ) — (6 ) Balance at December 31, 2017 $ (5 ) $ — $ (5 ) The following table presents the line items in our Consolidated Statements of Operations affected by reclassification adjustments out of AOCGL. Major Components of AOCGL Year Ended December 31, Consolidated Statements of 2017 2016 2015 (In thousands) Derivative financial instruments: Unrealized loss on FOREX contracts $ — $ — $ 7,829 Contract drilling, excluding depreciation Unrealized gain on Treasury Lock Agreements (8 ) (8 ) (8 ) Interest expense 2 3 (2,737 ) Income tax expense (benefit) $ (6 ) $ (5 ) $ 5,084 Net of tax Marketable securities: Unrealized loss on marketable securities $ — $ 11,600 $ — Other, net — — — Income tax expense $ — $ 11,600 $ — Net of tax

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies Various claims have been filed against us in the ordinary course of business, including claims by offshore workers alleging personal injuries. With respect to each claim or exposure, we have made an assessment, in accordance with GAAP, of the probability that the resolution of the matter would ultimately result in a loss. When we determine that an unfavorable resolution of a matter is probable and such amount of loss can be determined, we record a liability for the amount of the estimated loss at the time that both of these criteria are met. Our management believes that we have recorded adequate accruals for any liabilities that may reasonably be expected to result from these claims. Patent Litigation Ocean Blackhawk Ocean BlackHornet Ocean BlackRhino Ocean BlackLion Asbestos Litigation Other Litigation. Personal Injury Claims The Jones Act is a federal law that permits seamen to seek compensation for certain injuries during the course of their employment on a vessel and governs the liability of vessel operators and marine employers for the work-related injury or death of an employee. We engage outside consultants to assist us in estimating our aggregate liability for personal injury claims based on our historical losses and utilizing various actuarial models. We allocate a portion of the aggregate liability to “Accrued liabilities” based on an estimate of claims expected to be paid within the next twelve months with the residual recorded as “Other liabilities.” At December 31, 2017 our estimated liability for personal injury claims was $30.9 million, of which $5.2 million and $25.7 million were recorded in “Accrued liabilities” and “Other liabilities,” respectively, in our Consolidated Balance Sheets. At December 31, 2016 our estimated liability for personal injury claims was $32.9 million, of which $6.1 million and $26.8 million were recorded in “Accrued liabilities” and “Other liabilities,” respectively, in our Consolidated Balance Sheets. The eventual settlement or adjudication of these claims could differ materially from our estimated amounts due to uncertainties such as: • the severity of personal injuries claimed; • significant changes in the volume of personal injury claims; • the unpredictability of legal jurisdictions where the claims will ultimately be litigated; • inconsistent court decisions; and • the risks and lack of predictability inherent in personal injury litigation. Purchase Obligations Operating Leases. non-rig In addition, we lease certain blowout preventer equipment, or BOP, and related well control equipment under ten-year Letters of Credit and Other.

Sale and Leaseback Transactions

Sale and Leaseback Transactions	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Sale and Leaseback Transactions	12. Sale and Leaseback Transactions In February 2016, we entered into a ten-year In connection with the contractual services agreement with GE, we completed four sale and leaseback transactions with another GE affiliate during 2016 with respect to the Well Control Equipment on our four drillships. As a result of these transactions, we received an aggregate of $210.0 million in proceeds from the sale of the Well Control Equipment, which was less than the carrying value of the equipment. The resulting difference was recorded as prepaid rent with no gain or loss recognized on the transactions. The prepaid rent will be amortized over the respective terms of the operating leases. Future commitments under the operating leases and contractual services agreements are estimated to be approximately $65.0 million per year or an estimated $550.0 million in the aggregate over the remaining term of the agreements. During the years ended December 31, 2017 and 2016, we recognized $61.7 million and $34.0 million, respectively, in aggregate expense related to the Well Control Equipment leases and contractual services agreements.

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related-Party Transactions	13. Related-Party Transactions Transactions with Loews. out-of-pocket Transactions with Other Related Parties. Non-Executive Non-Executive

Restructuring and Separation Co

Restructuring and Separation Costs	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring and Separation Costs	14. Restructuring and Separation Costs In late 2017, in response to expectations that a recovery of the offshore drilling market will not occur in the near term, combined with changes to the size and composition of our drilling fleet since 2015, we reviewed our cost and organizational structure, including the way in which we market our services in certain countries. As a result, our management approved and initiated a reduction in workforce at our onshore bases and corporate facilities, as well as the negotiation of a termination of our agency agreement in Brazil, also referred to as the 2017 Reduction Plan. As of December 31, 2017, appropriate communications had been made to substantially all impacted personnel, and we incurred $14.1 million in restructuring and employee separation related costs during 2017. Accrued costs associated with the 2017 Reduction Plan were $13.6 million as of December 31, 2017, of which $11.5 million is related to the termination of our Brazilian agency agreement, which is expected to be paid in the first quarter of 2018, and $2.1 million is related to severance payments to two former executives, payable over a two year period. During 2015, in response to depressed conditions in the offshore drilling market at that time, we reviewed our cost and organization structure, and, as a result, our management approved and initiated a reduction in workforce at our onshore bases and corporate facilities, also referred to as the 2015 Reduction Plan. During 2015, we paid $9.8 million in restructuring and employee separation related costs to impacted personnel.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	15. Income Taxes On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act, commonly referred to as the Tax Reform Act. The Tax Reform Act amended the Internal Revenue Code in several areas that had a direct and immediate effect on our results of operations and statement of financial position as of and for the year ended December 31, 2017, including, among other items, a one-time one-time non-US Also on December 22, 2017, the Securities and Exchange Commission issued Staff Accounting Bulletin No. 118, which allows companies to report the income tax effects of the Tax Reform Act as a provisional amount based on a reasonable estimate, which would be subject to adjustment during a reasonable measurement period, not to exceed twelve months, until the accounting and analysis under ASC 740 is complete. Due to the timing of the enactment of the Tax Reform Act, there continues to be a significant amount of uncertainty as to the appropriate application of a number of the underlying provisions, pending further guidance and clarification from the relevant authorities. We will continue to monitor developments in this area and adjust our estimates throughout the year in 2018, as and if necessary, as additional guidance and clarification becomes available. Our provisional estimate of the tax effect of the Tax Reform Act is a net charge of $1.1 million as discussed above. We are still in the process of evaluating our estimate as it relates to the tax effect of (i) the mandatory, deemed repatriation aspect of the Tax Reform Act, (ii) the amount of deferred tax assets and liabilities subject to the income tax rate change from 35% to 21%, and (iii) the ability to more likely than not realize the benefit of deferred tax assets, including net operating losses and foreign tax credits. Any adjustments to these provisional amounts will be reported as a component of “Tax expense (benefit)” in the reporting period in which such adjustments are determined, which will be no later than the fourth quarter of 2018. Our income tax expense is a function of the mix between our domestic and international pre-tax The components of income tax expense (benefit) are as follows: Year Ended December 31, 2017 2016 2015 (In thousands) Federal — current $ 6,994 $ 230 $ 63,223 State — current 95 (60 ) 93 Foreign — current 25,252 10,297 71,655 Total current 32,341 10,467 134,971 Federal — deferred (85,066 ) (108,274 ) (245,045 ) Foreign — deferred 12,939 2,011 3,011 Total deferred (72,127 ) (106,263 ) (242,034 ) Total $ (39,786 ) $ (95,796 ) $ (107,063 ) The difference between actual income tax expense and the tax provision computed by applying the statutory federal income tax rate to income before taxes is attributable to the following: Year Ended December 31, 2017 2016 2015 (In thousands) Income before income tax expense: U.S. $ (241,178 ) $ (146,037 ) $ (11,158 ) Foreign 219,738 (322,262 ) (370,190 ) $ (21,440 ) $ (468,299 ) $ (381,348 ) Expected income tax benefit at federal statutory rate $ (7,504 ) $ (163,905 ) $ (133,472 ) Effect of tax rate changes (74,294 ) — — Mandatory repatriation of earnings pursuant to Tax Reform and Jobs Act 94,194 — — Effect of foreign operations (42,102 ) 48,573 (4,906 ) Amortization of deferred charges associated with intercompany rig sales to other tax jurisdictions — — 38,466 Valuation allowance (41,492 ) 62,400 — Uncertain tax positions, settlements and adjustments relating to prior years 31,726 (34,666 ) (1,114 ) Other (314 ) (8,198 ) (6,037 ) Income tax benefit $ (39,786 ) $ (95,796 ) $ (107,063 ) Deferred Income Taxes. December 31, 2017 2016 (In thousands) Deferred tax assets: Net operating loss carryforwards, or NOLs $ 133,298 $ 159,653 Foreign tax credits 27,623 95,145 Worker’s compensation and other current accruals 10,330 14,824 Bareboat charter deductions — 23,353 UK depreciation deduction 52,800 21,222 Anticipatory deductions and credits 13,111 — Deferred compensation 3,711 4,689 Foreign contribution taxes 3,806 3,857 Stock compensation awards 6,872 11,679 Deferred deductions 94 8,185 Other 3,748 2,526 Total deferred tax assets 255,393 345,133 Valuation allowance (169,224 ) (210,716 ) Net deferred tax assets 86,169 134,417 Deferred tax liabilities: Property, plant and equipment (236,038 ) (284,480 ) Mobilization (17,192 ) (46,274 ) Other (238 ) (674 ) Total deferred tax liabilities (253,468 ) (331,428 ) Net deferred tax liability $ (167,299 ) $ (197,011 ) We record a valuation allowance to derecognize a portion of our deferred tax assets, which we do not expect to be ultimately realized. A summary of changes in the valuation allowance is as follows: For the Year Ended December 31, 2017 2016 2015 (In thousands) Valuation allowance as of January 1 $ 210,716 $ 146,647 $ 48,036 Establishment of valuation allowances: Net operating losses 20,805 10,318 82,155 Foreign tax credits 2,877 62,400 — Other deferred tax assets 14,213 4,823 27,928 Releases of valuation allowances in various jurisdictions (79,387 ) (13,472 ) (11,472 ) Valuation allowance as of December 31 $ 169,224 $ 210,716 $ 146,647 Net Operating Loss Carryforwards Year Expiring Tax Benefit of Carryforwards (In millions) 2021 $ 5.1 2022 0.2 2023 0.1 2025 28.7 2027 7.6 2036 17.9 2037 0.2 Total $ 59.8 As of December 31, 2017, a valuation allowance for $110.9 million has been recorded for our NOLs for which the deferred tax assets are not likely to be realized. Foreign Tax Credits. Year Expiring Foreign Tax (In millions) 2019 $ 0.8 2024 3.1 2025 3.5 2026 20.0 2027 0.2 Total $ 27.6 As of December 31, 2017, a valuation allowance of $26.7 million has been recorded for our foreign tax credits for which the deferred tax assets are not likely to be realized. Valuation Allowances — Other Deferred Tax Assets. Unrecognized Tax Benefits. For the Year Ended December 31, 2017 2016 2015 (In thousands) Balance, beginning of period $ (34,970 ) $ (53,952 ) $ (57,116 ) Additions for current year tax positions (51,260 ) (4,233 ) (7,013 ) Additions for prior year tax positions (2,938 ) (1,020 ) (82 ) Reductions for prior year tax positions 623 19,661 2,673 Reductions related to statute of limitation expirations 6,681 4,574 7,586 Balance, end of period $ (81,864 ) $ (34,970 ) $ (53,952 ) The $51.3 million addition to current year tax positions for 2017 is primarily attributable to a provisional liability associated with the use of tax attributes in conjunction with the deemed, mandatory repatriation provision of the Tax Reform Act. The $19.7 million reduction for prior year tax positions in 2016 resulted primarily from the devaluation of the Egyptian Pound. At December 31, 2017, $2.3 million, $51.3 million and $52.9 million of the net liability for uncertain tax positions were reflected in “Other assets,” “Deferred tax liability” and “Other liabilities,” respectively. At December 31, 2016, $2.1 million, $3.1 million and $35.0 million of the net liability for uncertain tax positions were reflected in “Other assets,” “Deferred tax liability” and “Other liabilities,” respectively. Of the net unrecognized tax benefits at December 31, 2017, 2016 and 2015, all $101.9 million, $36.0 million and $49.4 million, respectively, would affect the effective tax rates if recognized. At December 31, 2017, the amount of accrued interest and penalties related to uncertain tax positions were $3.1 million and $15.1 million, respectively. At December 31, 2016, the amount of accrued interest and penalties related to uncertain tax positions were $2.7 million and $16.8 million, respectively. We record interest related to accrued uncertain tax positions in interest expense and recognize penalties associated with uncertain tax positions in tax expense. Interest expense (benefit) recognized during the three years ended December 31, 2017 related to uncertain tax positions was $0.5 million, $(0.1) million and $(4.8) million, respectively. Penalties recognized during the three years ended December 31, 2017 related to uncertain tax positions were $(1.7) million, $(23.2) million and $2.3 million, respectively. In several of the international locations in which we operate, certain of our wholly-owned subsidiaries enter into agreements with other of our wholly-owned subsidiaries to provide specialized services and equipment in support of our foreign operations. We apply a transfer pricing methodology to determine the amount to be charged for providing the services and equipment. In most cases, there are alternative transfer pricing methodologies that could be applied to these transactions and, if applied, could result in different chargeable amounts. Taxing authorities in the various foreign locations in which we operate could apply one of the alternative transfer pricing methodologies which could result in an increase to our income tax liabilities with respect to tax returns that remain subject to examination. We expect the statute of limitations for the 2012 tax year to expire in 2018 for one of our subsidiaries operating in Mexico. We anticipate that the related unrecognized tax benefit will decrease by $1.5 million at that time. Tax Returns and Examinations.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Postemployment Benefits [Abstract]
Employee Benefit Plans	16. Employee Benefit Plans Defined Contribution Plans We maintain defined contribution retirement plans for our U.S., U.K. and third-country national, or TCN, employees. The plan for our U.S. employees, or the 401k Plan, is designed to qualify under Section 401(k) of the Code. Under the 401k Plan, each participant may elect to defer taxation on a portion of his or her eligible earnings, as defined by the 401k Plan, by directing his or her employer to withhold a percentage of such earnings. A participating employee may also elect to make after-tax The defined contribution retirement plan for our U.K. employees provides that we make annual contributions in an amount equal to the employee’s contributions generally up to a maximum percentage of the employee’s defined compensation per year. Our contribution during 2017 and from July 1, 2016 to December 31, 2016 for employees working in the U.K. sector of the North Sea was 6% of the employee’s defined compensation. During the first six months of 2016 and in 2015, our contribution was 10% of the employee’s defined compensation. Our provision for contributions was $1.4 million, $2.0 million and $3.4 million for the years ended December 31, 2017, 2016 and 2015, respectively. The defined contribution retirement plan for our TCN employees, or International Savings Plan, is similar to the 401k Plan. During 2017, 2016 and 2015, we matched 5%, 6% and 6%, respectively, of each employee’s compensation contributed to the International Savings Plan. During the four months ended April 30, 2015, we made discretionary profit sharing contributions to the International Savings Plan equal to 4% of a participant’s defined compensation. We ceased making profit sharing contributions on May 1, 2015. Our provision for contributions was $0.4 million, $0.8 million and $2.2 million for 2017, 2016 and 2015, respectively. Deferred Compensation and Supplemental Executive Retirement Plan Our Amended and Restated Diamond Offshore Management Company Supplemental Executive Retirement Plan, or Supplemental Plan, provides benefits to a select group of our management or other highly compensated employees to compensate such employees for any portion of our base salary contribution and/or matching contribution under the 401k Plan that could not be contributed to that plan because of limitations within the Code. Our provision for contributions to the Supplemental Plan for 2017, 2016 and 2015 was approximately $136,000, $146,000 and $153,000, respectively.

Segments and Geographic Area An

Segments and Geographic Area Analysis	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segments and Geographic Area Analysis	17. Segments and Geographic Area Analysis Although we provide contract drilling services with different types of offshore drilling rigs and also provide such services in many geographic locations, we have aggregated these operations into one reportable segment based on the similarity of economic characteristics due to the nature of the revenue-earning process as it relates to the offshore drilling industry over the operating lives of our drilling rigs. Revenues from contract drilling services by equipment-type are listed below: Year Ended December 31, 2017 2016 2015 (In thousands) Floaters: Ultra-Deepwater $ 1,090,139 $ 989,158 $ 1,339,059 Deepwater 202,329 256,997 548,667 Mid-Water 137,607 248,846 387,549 Total Floaters 1,430,075 1,495,001 2,275,275 Jack-ups 21,144 30,213 84,909 Total contract drilling revenues 1,451,219 1,525,214 2,360,184 Revenues related to reimbursable expenses 34,527 75,128 59,209 Total revenues $ 1,485,746 $ 1,600,342 $ 2,419,393 Geographic Areas Our drilling rigs are highly mobile and may be moved to other markets throughout the world in response to market conditions or customer needs. At December 31, 2017, our actively-marketed drilling rigs were located offshore four countries in addition to the United States. Revenues by geographic area are presented by attributing revenues to the individual country or areas where the services were performed. Year Ended December 31, 2017 2016 2015 (In thousands) United States $ 630,595 $ 548,024 $ 513,605 International: South America 348,479 434,956 812,271 Australia/Asia 307,925 234,182 415,033 Europe 177,603 344,964 532,824 Mexico 21,144 38,216 145,660 855,151 1,052,318 1,905,788 Total revenues $ 1,485,746 $ 1,600,342 $ 2,419,393 An individual international country may, from time to time, comprise a material percentage of our total contract drilling revenues from unaffiliated customers. For the years ended December 31, 2017, 2016 and 2015, individual countries that comprised 5% or more of our total contract drilling revenues from unaffiliated customers are listed below. Year Ended December 31, 2017 2016 2015 Brazil 18.9 % 18.0 % 23.1 % United Kingdom 12.0 % 15.3 % 11.4 % Malaysia 11.2 % 1.7 % 6.8 % Australia 9.5 % 12.8 % 7.0 % Trinidad & Tobago 4.6 % 9.2 % 9.8 % Mexico 1.4 % 2.4 % 6.0 % Romania — 4.0 % 9.7 % The following table presents our long-lived tangible assets by geographic location as of December 31, 2017, 2016 and 2015. A substantial portion of our assets is comprised of rigs that are mobile, and therefore asset locations at the end of the period are not necessarily indicative of the geographic distribution of the earnings generated by such assets during the periods and may vary from period to period due to the relocation of rigs. In circumstances where our drilling rigs were in transit at the end of a calendar year, they have been presented in the tables below within the geographic area in which they were expected to operate. December 31, 2017 (1) 2016 (1) 2015 (1) (In thousands) Drilling and other property and equipment, net: United States $ 2,300,956 $ 2,753,511 $ 3,292,474 International: Australia/Asia/Middle East 1,714,246 1,429,563 1,224,089 South America 923,398 1,030,069 1,051,283 Europe/Africa 320,473 380,462 664,520 Mexico 2,568 133,330 146,448 2,960,685 2,973,424 3,086,340 Total $ 5,261,641 $ 5,726,935 $ 6,378,814 (1) During 2017, 2016 and 2015, we recorded aggregate impairment losses of $99.3 million, $678.1 million and $860.4 million, respectively, to write down certain of our drilling rigs and related equipment with indicators of impairment to their estimated recoverable amounts. The following table presents the countries in which material concentrations of our long-lived tangible assets were located as of December 31, 2017, 2016 and 2015: December 31, 2017 2016 2015 United States 43.7 % 48.1 % 51.6 % Malaysia 20.6 % 13.6 % 10.4 % Brazil 17.5 % 16.8 % 15.3 % Australia 12.0 % 11.4 % 4.5 % As of December 31, 2017, 2016 and 2015, no other countries had more than a 5% concentration of our long-lived tangible assets. Major Customers Our customer base includes major and independent oil and gas companies and government-owned oil companies. Revenues from our major customers for the years ended December 31, 2017, 2016 and 2015 that contributed more than 10% of our total revenues are as follows: Year Ended December 31, Customer 2017 2016 2015 Anadarko 24.9 % 22.4 % 12.4 % Petróleo Brasileiro S.A. 18.9 % 17.9 % 24.1 % Hess Corporation 16.0 % 7.7 % 0.3 % BP 15.8 % 9.0 % 0.1 % ExxonMobil — 5.8 % 12.4 %

Unaudited Quarterly Financial D

Unaudited Quarterly Financial Data	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Unaudited Quarterly Financial Data	18. Unaudited Quarterly Financial Data Unaudited summarized financial data by quarter for the years ended December 31, 2017 and 2016 is shown below. First Second Third Fourth (In thousands, except per share data) 2017 Revenues $ 374,226 $ 399,289 $ 366,023 $ 346,208 Operating income (loss) (1) 50,859 20,824 58,581 (6,385 ) Income (loss) before income tax expense 24,462 (7,020 ) (3,801 ) (35,081 ) Net income (loss) 23,539 15,949 10,799 (31,941 ) Net income (loss) per share, basic and diluted $ 0.17 $ 0.12 $ 0.08 $ (0.23 ) 2016 Revenues $ 470,543 $ 388,747 $ 349,178 $ 391,874 Operating income (loss) (2) 111,569 (626,669 ) 54,071 104,145 Income (loss) before income tax expense 83,196 (666,115 ) 34,746 79,874 Net income (loss) 87,425 (589,937 ) 13,927 116,082 Net income (loss) per share, basic and diluted $ 0.64 $ (4.30 ) $ 0.10 $ 0.85 (1) During the second and fourth quarters of 2017, we recognized an aggregate impairment loss of $71.2 million and $28.0 million, respectively, to write down certain of our drilling rigs with indicators of impairment to their estimated recoverable amounts. See Notes 1 and 2. (2) During the second quarter of 2016, we recognized an aggregate impairment loss of $678.1 million to write down certain of our drilling rigs and related spare parts with indicators of impairment to their estimated recoverable amounts. See Notes 1 and 2.

General Information (Policies)

General Information (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation Our consolidated financial statements include the accounts of Diamond Offshore Drilling, Inc. and our wholly-owned subsidiaries after elimination of intercompany transactions and balances.
Use of Estimates in the Preparation of Financial Statements	Use of Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with accounting principles generally accepted in the United States, or U.S., or GAAP, 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 amount of revenues and expenses during the reporting period. Actual results could differ from those estimated.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider short-term, highly liquid investments that have an original maturity of three months or less and deposits in money market mutual funds that are readily convertible into cash to be cash equivalents. The effect of exchange rate changes on cash balances held in foreign currencies was not material for the years ended December 31, 2017, 2016 and 2015.
Provision for Bad Debts	Provision for Bad Debts We record a provision for bad debts on a case-by-case
Assets Held For Sale	Assets Held For Sale We reported the $96.3 million and $0.4 million carrying values of certain of our rigs being marketed for sale as “Assets held for sale” in our Consolidated Balance Sheets at December 31, 2017 and 2016, respectively. The Ocean Victory Ocean Scepter jack-up Ocean Spur
Drilling and Other Property and Equipment	Drilling and Other Property and Equipment We carry our drilling and other property and equipment at cost, less accumulated depreciation. Maintenance and routine repairs are charged to income currently while replacements and betterments that upgrade or increase the functionality of our existing equipment and that significantly extend the useful life of an existing asset are capitalized. Significant judgments, assumptions and estimates may be required in determining whether or not such replacements and betterments meet the criteria for capitalization and in determining useful lives and salvage values of such assets. Changes in these judgments, assumptions and estimates could produce results that differ from those reported. During the years ended December 31, 2017 and 2016, we capitalized $69.4 million and $177.6 million, respectively, in replacements and betterments of our drilling fleet. Costs incurred for major rig upgrades and/or the construction of rigs are accumulated in construction work-in-progress,
Capitalized Interest	Capitalized Interest We capitalize interest cost for rig construction or upgrades, as well as other qualifying projects. During the three years ended December 31, 2017, we capitalized interest on qualifying expenditures, primarily related to our rig construction projects. A reconciliation of our total interest cost to “Interest expense, net of amounts capitalized” as reported in our Consolidated Statements of Operations is as follows: For the Year Ended December 31, 2017 2016 2015 (In thousands) Total interest cost including amortization of debt issuance costs $ 113,618 $ 110,748 $ 110,242 Capitalized interest (90 ) (20,814 ) (16,308 ) Total interest expense as reported $ 113,528 $ 89,934 $ 93,934
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets We evaluate our property and equipment for impairment whenever changes in circumstances indicate that the carrying amount of an asset may not be recoverable (such as, but not limited to, cold stacking a rig, the expectation of cold stacking a rig in the near term, contracted backlog of less than one year for a rig, a decision to retire or scrap a rig, or excess spending over budget on a newbuild, construction project or major rig upgrade). We utilize an undiscounted probability-weighted cash flow analysis in testing an asset for potential impairment. Our assumptions and estimates underlying this analysis include the following: • dayrate by rig; • utilization rate by rig if active, warm stacked or cold stacked (expressed as the actual percentage of time per year that the rig would be used at certain dayrates); • the per day operating cost for each rig if active, warm stacked or cold stacked; • the estimated annual cost for rig replacements and/or enhancement programs; • the estimated maintenance, inspection or other reactivation costs associated with a rig returning to work; • salvage value for each rig; and • estimated proceeds that may be received on disposition of each rig. Based on these assumptions, we develop a matrix for each rig under evaluation using multiple utilization/dayrate scenarios, to each of which we have assigned a probability of occurrence. We arrive at a projected probability-weighted cash flow for each rig based on the respective matrix and compare such amount to the carrying value of the asset to assess recoverability. The underlying assumptions and assigned probabilities of occurrence for utilization and dayrate scenarios are 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, inspection and reactivation costs, are estimated using historical data adjusted for known developments, cost projections for re-entry Management’s assumptions are necessarily subjective and are an inherent part of our asset impairment evaluation , oil-producing
Fair Value of Financial Instruments	Fair Value of Financial Instruments We believe that the carrying amount of our current financial instruments approximates fair value because of the short maturity of these instruments. See Note 7.
Debt Issuance Costs	Debt Issuance Costs Deferred costs associated with our senior notes are presented in our Consolidated Balance Sheets at December 31, 2017 and 2016 as a reduction in the related long-term debt and are amortized over the respective terms of the related debt. See Note 9.
Income Taxes	Income Taxes We account for income taxes in accordance with accounting standards that require the recognition of the amount of taxes payable or refundable for the current year and an asset and liability approach in recognizing the amount of deferred tax liabilities and assets for the future tax consequences of events that have been currently recognized in our financial statements or tax returns. In each of our tax jurisdictions we recognize a current tax liability or asset for the estimated taxes payable or refundable on tax returns for the current year and a deferred tax asset or liability for the estimated future tax effects attributable to temporary differences and carryforwards. Deferred tax assets are reduced by a valuation allowance, if necessary, which is determined by the amount of any tax benefits that, based on available evidence, are not expected to be realized under a “more likely than not” approach. Deferred tax assets and liabilities are classified as noncurrent in a classified statement of financial position. We make judgments regarding future events and related estimates especially as they pertain to the forecasting of our effective tax rate, the potential realization of deferred tax assets such as utilization of foreign tax credits, and exposure to the disallowance of items deducted on tax returns upon audit. We record interest related to accrued unrecognized tax positions in “Interest expense, net of amounts capitalized” and recognize penalties associated with uncertain tax positions in “Income tax benefit” in our Consolidated Statements of Operations. Liabilities for uncertain tax positions, including any penalty, are denominated in the currency of the related tax jurisdiction and are revalued for changes in currency exchange rates. The revaluation of such liabilities for uncertain tax positions is reported in “Income tax benefit” in our Consolidated Statements of Operations. See Note 15.
Treasury Stock	Treasury Stock In connection with the vesting of restricted stock units held by certain individuals, we acquired 29,416 and 7,923 shares of our common stock during 2017 and 2016, respectively (valued at $0.5 million in 2017 and $0.2 million in 2016), in satisfaction of tax withholding obligations that were incurred on the vesting date. See Note 4. Depending on market conditions, we may, from time to time, purchase shares of our common stock in the open market or otherwise. We account for the purchase of treasury stock using the cost method, which reports the cost of the shares acquired in “Treasury stock” as a deduction from stockholders’ equity in our Consolidated Balance Sheets. We did not repurchase any shares of our outstanding common stock during 2017, 2016 or 2015.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is the change in equity of a business enterprise during a period from transactions and other events and circumstances except those transactions resulting from investments by owners and distributions to owners. Comprehensive income (loss) for the three years ended December 31, 2017, 2016 and 2015 includes net income (loss) and unrealized holding gains and losses on marketable securities and financial derivatives designated as cash flow accounting hedges. See Note 10.
Foreign Currency	Foreign Currency Our functional currency is the U.S. dollar. Transactions incurred in currencies other than the U.S. dollar are subject to gains or losses due to fluctuations in those currencies. We report foreign currency transaction gains and losses as “Foreign currency transaction (loss) gain” in our Consolidated Statements of Operations and may also include, when applicable, unrealized gains and losses to record the carrying value of foreign currency forward exchange, or FOREX, contracts not designated as accounting hedges and realized gains and losses from the settlement of such contracts. The revaluation of assets and liabilities related to foreign income taxes, including deferred tax assets and liabilities and uncertain tax positions, including any penalty, is reported in “Income tax benefit (expense)” in our Consolidated Statements of Operations.
Revenue Recognition	Revenue Recognition We recognize revenue from dayrate drilling contracts as services are performed. In connection with such drilling contracts, we may receive fees (on either a lump-sum Some of our drilling contracts require downtime before the start of the contract to prepare the rig to meet customer requirements. At times, we may be compensated by the customer for such work (on either a lump-sum From time to time, we may receive fees from our customers for capital improvements to our rigs (on either a lump-sum We record reimbursements received for the purchase of supplies, equipment, personnel services and other services provided at the request of our customers in accordance with a contract or agreement, for the gross amount billed to the customer, as “Revenues related to reimbursable expenses” in our Consolidated Statements of Operations.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In October 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory, 2016-16. 2016-16 2016-16. 2016-16 In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments 2016-15. 2016-15 zero-coupon 2016-15 2016-15 2016-15 In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) 2016-02, non-lease 2016-02, 2016-02 Non-lease 2014-09. 2016-02 2016-02 2016-02 2016-02, In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09, 2014-09 2014-09 2014-09

General Information (Tables)

General Information (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Reconciliation of Total Interest Cost to Interest Expense	A reconciliation of our total interest cost to “Interest expense, net of amounts capitalized” as reported in our Consolidated Statements of Operations is as follows: For the Year Ended December 31, 2017 2016 2015 (In thousands) Total interest cost including amortization of debt issuance costs $ 113,618 $ 110,748 $ 110,242 Capitalized interest (90 ) (20,814 ) (16,308 ) Total interest expense as reported $ 113,528 $ 89,934 $ 93,934

Supplemental Financial Inform29

Supplemental Financial Information (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts Receivable, Net of Allowance for Doubtful Accounts	Accounts receivable, net of allowance for bad debts, consists of the following: December 31, 2017 2016 (In thousands) Trade receivables $ 247,453 $ 236,040 Value added tax receivables 14,067 14,639 Related party receivables 205 149 Other 464 1,659 262,189 252,487 Allowance for bad debts (5,459 ) (5,459 ) Total $ 256,730 $ 247,028
Changes in Provision for Bad Debts	An analysis of the changes in our provision for bad debts for each of the three years ended December 31, 2017, 2016 and 2015 is as follows: For the Year Ended December 31, 2017 2016 2015 (In thousands) Allowance for bad debts, beginning of year $ 5,459 $ 5,724 $ 5,724 Bad debt recovery — (265 ) — Allowance for bad debts, end of year $ 5,459 $ 5,459 $ 5,724
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following: December 31, 2017 2016 (In thousands) Rig spare parts and supplies $ 28,383 $ 25,343 Deferred mobilization costs 51,297 61,488 Prepaid BOP Lease 3,873 3,873 Prepaid insurance 3,091 3,771 Prepaid taxes 67,212 2,894 Other 3,769 4,777 Total $ 157,625 $ 102,146
Accrued Liabilities	Accrued liabilities consist of the following: December 31, 2017 2016 (In thousands) Rig operating expenses $ 48,894 $ 33,732 Payroll and benefits 46,560 45,619 Deferred revenue 11,371 9,522 Accrued capital project/upgrade costs 3,698 60,308 Interest payable 28,234 18,365 Personal injury and other claims 5,699 6,424 Other 10,199 8,189 Total $ 154,655 $ 182,159
Noncash Investing and Financing Activities	Noncash investing activities excluded from the Consolidated Statements of Cash Flows and other supplemental cash flow information is as follows: December 31, 2017 2016 2015 (In thousands) Accrued but unpaid capital expenditures at period end $ 3,698 $ 60,308 $ 84,146 Common stock withheld for payroll tax obligations (1) 483 181 236 Cash interest payments (2) 97,096 105,987 110,412 Cash income taxes paid (refunded), net: U.S. federal — (31,151 ) (21,751 ) Foreign 43,999 48,931 69,697 State 94 1 58 (1) Represents the cost of 29,416 and 7,923 shares of common stock withheld to satisfy the payroll tax obligation incurred as a result of the vesting of restricted stock units in 2017 and 2016, respectively. These costs are presented as a deduction from stockholders’ equity in “Treasury stock” in our Consolidated Balance Sheets at December 31, 2017 and 2016. (2) Interest payments, net of amounts capitalized, were $97.0 million, $86.1 million and $94.7 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Retrospective Effect of Adoption that Impacted on Balance Sheets	The impact to our Consolidated Balance Sheets is as follows: Retained Additional Paid-in Capital (In thousands) Balance as of January 1, 2017 before adoption $ 1,946,765 $ 2,004,514 Adjustment for making election to account for forfeitures as they occur (634 ) 634 Balance as of January 1, 2017 after adoption $ 1,946,131 $ 2,005,148
Summary of Activity Under Stock Plan	The fair value of SARs granted under the Equity Plan (or its predecessor) during each of the years ended December 31, 2017, 2016 and 2015 was estimated using the Black Scholes pricing model with the following weighted average assumptions: Year Ended December 31, 2017 2016 2015 Expected life of SARs (in years) 7 7 6 Expected volatility 31.70 % 45.79 % 55.12 % Dividend yield — .60 % (1) 1.70 % Risk free interest rate 2.09 % 1.46 % 1.66 % (1) Represents dividend yield related to January 2016 grant of SARs prior to our decision in early 2016 to discontinue paying dividends.
Weighted Average Assumptions Used in Estimating Fair Value of Options and SARs	A summary of SARs activity under the Equity Plan as of December 31, 2017 and changes during the year then ended is as follows: Number of Weighted- Weighted- (Years) Aggregate Intrinsic (In Thousands) Awards outstanding at January 1, 2017 1,449,706 $ 67.43 Granted 66,000 $ 14.95 Exercised — Forfeited 5,240 $ 41.88 Expired 248,352 $ 90.95 Awards outstanding at December 31, 2017 1,262,114 $ 60.16 4.3 $ 272 Awards exercisable at December 31, 2017 1,230,382 $ 60.63 4.2 $ 272
Time-vesting RSUs [Member]
Summary of Restricted Stock Units Awarded Under Equity Plan	A summary of activity for time-vesting RSUs under the Equity Plan as of December 31, 2017 and changes during the year then ended is as follows: Number of Weighted- Nonvested awards at January 1, 2017 319,560 $ 23.13 Granted 276,085 $ 16.37 Vested 68,659 $ 25.08 Forfeited 55,697 $ 20.76 Nonvested awards at December 31, 2017 471,289 $ 19.15
Performance-Vesting RSUs [Member]
Summary of Restricted Stock Units Awarded Under Equity Plan	A summary of activity for performance-vesting RSUs under the Equity Plan as of December 31, 2017 and changes during the year then ended is as follows: Number of Weighted- Nonvested awards at January 1, 2017 431,706 $ 24.55 Granted 370,616 $ 16.61 Vested 18,876 $ 46.64 Forfeited 55,590 $ 19.95 Nonvested awards at December 31, 2017 727,856 $ 20.28

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Reconciliation of Numerators and Denominators of Basic and Diluted Per-Share Computations	A reconciliation of the numerators and the denominators of the basic and diluted per-share Year Ended December 31, 2017 2016 2015 (In thousands, except per share data) Net income (loss) — basic and diluted (numerator): $ 18,346 $ (372,503 ) $ (274,285 ) Weighted-average shares — basic (denominator): 137,213 137,168 137,157 Dilutive effect of stock-based awards 52 — — Weighted-average shares including conversions — diluted (denominator): 137,265 137,168 137,157 Earnings (loss) per share: Basic $ 0.13 $ (2.72 ) $ (2.00 ) Diluted $ 0.13 $ (2.72 ) $ (2.00 )
Securities Excluded from Computation of Diluted Earning (Loss) Per Share	The following table sets forth the share effects of stock-based awards excluded from the computation of earnings (loss) per share, as the inclusion of such potentially dilutive shares would have been antidilutive for the periods presented. Year Ended December 31, 2017 2016 2015 (In thousands) Employee and director: Stock options — 7 26 SARs 1,315 1,505 1,553 RSUs 757 704 278

Derivative Financial Instrume32

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Amounts Recognized in Consolidated Balance Sheets and Consolidated Statements of Operations Related to Derivative Financial Instruments Designated as Cash Flow Hedges	The following table presents the amounts recognized in our Consolidated Balance Sheets and Consolidated Statements of Operations related to our derivative financial instruments designated as cash flow hedges for the year ended December 31, 2015. For the Year Ended 2015 (In thousands) FOREX contracts: Amount of loss recognized in AOCGL on derivative (effective portion) $ (2,420) Location of loss reclassified from AOCGL into income (effective portion) Contract drilling, Amount of loss reclassified from AOCGL into income (effective portion) $ (7,829) Location of loss recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing) Foreign currency Amount of loss recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing) $ (1)

Financial Instruments and Fai33

Financial Instruments and Fair Value Disclosures (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on Recurring and Nonrecurring Basis	Assets and liabilities measured at fair value are summarized below. December 31, 2017 Fair Value Measurements Using Assets at Fair Total Losses for Year Ended (1) Level 1 Level 2 Level 3 (In thousands) Recurring fair value measurements: Assets: Short-term investments $ 358,019 $ — $ — $ 358,019 Nonrecurring fair value measurements: Assets: Impaired assets (2) $ — $ — $ 97,261 $ 97,261 $ 99,313 (1) Represents impairment losses of $71.3 million and $28.0 million recognized during the second and fourth quarters of 2017, respectively, related to our 2017 Impaired Rigs. See Note 2. (2) Represents the total book value as of December 31, 2017 of one ultra-deepwater rig and one deepwater semisubmersible rig, which were written down to their estimated fair value during the second quarter of 2017, and one jack-up December 31, 2016 Fair Value Measurements Using Assets at Fair Total Losses for Year Ended (1) Level 1 Level 2 Level 3 (In thousands) Recurring fair value measurements: Assets: Short-term investments $ 146,360 $ — $ — $ 146,360 Mortgage-backed securities — 35 — 35 Total assets $ 146,360 $ 35 $ — $ 146,395 Nonrecurring fair value measurements: Assets: Impaired assets (2) $ — $ — $ 69,153 $ 69,153 $ 678,145 (1) Represents impairment losses of $8.1 million and $670.0 million recognized during the year ended December 31, 2016 related to our rig spare parts and supplies and 2016 Impaired Rigs, respectively. See Notes 2 and 3. (2) Represents the total book value as of December 31, 2016 for 11 drilling rigs ($45.5 million) and for rig spare parts and supplies ($23.6 million), which were previously written down to their estimated fair value. Of the total fair value, $23.6 million, $0.4 million and $45.1 million were reported as “Prepaid expenses and other current assets,” “Assets held for sale” and “Drilling and other property and equipment, net of accumulated depreciation,” respectively, in our Consolidated Balance Sheets at December 31, 2016. See Notes 1, 2 and 3.
Fair Values and Related Carrying Values of Our Debt Instruments	December 31, 2017 December 31, 2016 Fair Value Carrying Value Fair Value Carrying Value (In millions) 5.875% Senior Notes due 2019 $ — $ — $ 518.6 $ 499.8 3.45% Senior Notes due 2023 223.1 249.4 215.0 249.3 7.875% Senior Notes due 2025 523.1 496.5 — — 5.70% Senior Notes due 2039 405.0 497.2 392.5 497.1 4.875% Senior Notes due 2043 547.5 748.9 532.7 748.9

Drilling and Other Property a34

Drilling and Other Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Summary of Cost and Accumulated Depreciation of Drilling and Other Property and Equipment	Cost and accumulated depreciation of drilling and other property and equipment are summarized as follows: December 31, 2017 2016 (In thousands) Drilling rigs and equipment $ 7,971,406 $ 8,950,385 Land and buildings 63,309 64,449 Office equipment and other 82,691 73,108 Cost 8,177,406 9,087,942 Less accumulated depreciation (2,855,765 ) (3,361,007 ) Drilling and other property and equipment, net $ 5,261,641 $ 5,726,935

Credit Agreement and Senior N35

Credit Agreement and Senior Notes (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Summary of Senior Notes	At December 31, 2017, our senior notes were comprised of the following debt issues: Principal Amount Interest Rate Semiannual Interest Payment Dates Debt Issue (In millions) Maturity Date Coupon Effective 3.45% Senior Notes due 2023 $ 250.0 November 1, 2023 3.45% 3.50% May 1 and November 1 7.875% Senior Notes due 2025 $ 500.0 August 15, 2025 7.875% 8.00% February 15 and August 15 5.70% Senior Notes due 2039 $ 500.0 October 15, 2039 5.70% 5.75% April 15 and October 15 4.875% Senior Notes due 2043 $ 750.0 November 1, 2043 4.875% 4.89% May 1 and November 1
Summary of Carrying Value of Senior Notes, Net of Unamortized Discount and Debt Issuance Costs	At December 31, 2017 and 2016, the carrying value of our senior notes, net of unamortized discount and debt issuance costs, was as follows: December 31, 2017 2016 (In thousands) 5.875% Senior Notes due 2019 $ — $ 498,679 3.45% Senior Notes due 2023 248,162 247,879 7.875% Senior Notes due 2025 489,420 — 5.70% Senior Notes due 2039 492,971 492,812 4.875% Senior Notes due 2043 741,672 741,514 Total senior notes, net $ 1,972,225 $ 1,980,884
Aggregate Maturities of Senior Notes, Excluding Net Unamortized Discounts and Debt Issuance Costs	As of December 31, 2017, the aggregate annual maturity of our senior notes, excluding net unamortized discounts and debt issuance costs of $8.1 million and $19.7 million, respectively, was as follows: Aggregate (In thousands) Year Ending December 31, 2018 $ — 2019 — 2020 — 2021 — 2022 — Thereafter 2,000,000 Total maturities of senior notes $ 2,000,000

Other Comprehensive Income (L36

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Components of Other Comprehensive Gain (Loss) and Related Income Tax Effects	The following table sets forth the components of “Other comprehensive gain (loss)” and the related income tax effects thereon for the three years ended December 31, 2017 and the cumulative balances in AOCGL by component at December 31, 2017, 2016 and 2015. Unrealized Gain (Loss) on Total AOCGL Derivative Marketable (In thousands) Balance at January 1, 2015 (3,504 ) (101 ) (3,605 ) Change in other comprehensive loss before reclassifications, after tax of $846 and $(1) (1,574 ) (4,940 ) (6,514 ) Reclassification adjustments for items included in Net Loss, after tax of $(2,737) and $0 5,084 — 5,084 Total other comprehensive income (loss) 3,510 (4,940 ) (1,430 ) Balance at December 31, 2015 6 (5,041 ) (5,035 ) Change in other comprehensive loss before reclassifications, after tax of $0 and $2 — (6,559 ) (6,559 ) Reclassification adjustments for items included in Net Loss, after tax of $3 and $0 (5 ) 11,600 11,595 Total other comprehensive (loss) income (5 ) 5,041 5,036 Balance at December 31, 2016 1 — 1 Reclassification adjustments for items included in Net Loss, after tax of $2 and $0 (6 ) — (6 ) Total other comprehensive loss (6 ) — (6 ) Balance at December 31, 2017 $ (5 ) $ — $ (5 )
Items in Consolidated Statements of Operations Affected by Reclassification Adjustments	The following table presents the line items in our Consolidated Statements of Operations affected by reclassification adjustments out of AOCGL. Major Components of AOCGL Year Ended December 31, Consolidated Statements of 2017 2016 2015 (In thousands) Derivative financial instruments: Unrealized loss on FOREX contracts $ — $ — $ 7,829 Contract drilling, excluding depreciation Unrealized gain on Treasury Lock Agreements (8 ) (8 ) (8 ) Interest expense 2 3 (2,737 ) Income tax expense (benefit) $ (6 ) $ (5 ) $ 5,084 Net of tax Marketable securities: Unrealized loss on marketable securities $ — $ 11,600 $ — Other, net — — — Income tax expense $ — $ 11,600 $ — Net of tax

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components of Income Tax Expense (Benefit)	The components of income tax expense (benefit) are as follows: Year Ended December 31, 2017 2016 2015 (In thousands) Federal — current $ 6,994 $ 230 $ 63,223 State — current 95 (60 ) 93 Foreign — current 25,252 10,297 71,655 Total current 32,341 10,467 134,971 Federal — deferred (85,066 ) (108,274 ) (245,045 ) Foreign — deferred 12,939 2,011 3,011 Total deferred (72,127 ) (106,263 ) (242,034 ) Total $ (39,786 ) $ (95,796 ) $ (107,063 )
Difference Between Actual Income Tax Expense and Tax Provision Computed by Applying Statutory Federal Income Tax Rate to Income Before Taxes	The difference between actual income tax expense and the tax provision computed by applying the statutory federal income tax rate to income before taxes is attributable to the following: Year Ended December 31, 2017 2016 2015 (In thousands) Income before income tax expense: U.S. $ (241,178 ) $ (146,037 ) $ (11,158 ) Foreign 219,738 (322,262 ) (370,190 ) $ (21,440 ) $ (468,299 ) $ (381,348 ) Expected income tax benefit at federal statutory rate $ (7,504 ) $ (163,905 ) $ (133,472 ) Effect of tax rate changes (74,294 ) — — Mandatory repatriation of earnings pursuant to Tax Reform and Jobs Act 94,194 — — Effect of foreign operations (42,102 ) 48,573 (4,906 ) Amortization of deferred charges associated with intercompany rig sales to other tax jurisdictions — — 38,466 Valuation allowance (41,492 ) 62,400 — Uncertain tax positions, settlements and adjustments relating to prior years 31,726 (34,666 ) (1,114 ) Other (314 ) (8,198 ) (6,037 ) Income tax benefit $ (39,786 ) $ (95,796 ) $ (107,063 )
Components of Deferred Income Tax Assets and Liabilities	Deferred Income Taxes. December 31, 2017 2016 (In thousands) Deferred tax assets: Net operating loss carryforwards, or NOLs $ 133,298 $ 159,653 Foreign tax credits 27,623 95,145 Worker’s compensation and other current accruals 10,330 14,824 Bareboat charter deductions — 23,353 UK depreciation deduction 52,800 21,222 Anticipatory deductions and credits 13,111 — Deferred compensation 3,711 4,689 Foreign contribution taxes 3,806 3,857 Stock compensation awards 6,872 11,679 Deferred deductions 94 8,185 Other 3,748 2,526 Total deferred tax assets 255,393 345,133 Valuation allowance (169,224 ) (210,716 ) Net deferred tax assets 86,169 134,417 Deferred tax liabilities: Property, plant and equipment (236,038 ) (284,480 ) Mobilization (17,192 ) (46,274 ) Other (238 ) (674 ) Total deferred tax liabilities (253,468 ) (331,428 ) Net deferred tax liability $ (167,299 ) $ (197,011 )
Summary of Changes in Valuation Allowance	A summary of changes in the valuation allowance is as follows: For the Year Ended December 31, 2017 2016 2015 (In thousands) Valuation allowance as of January 1 $ 210,716 $ 146,647 $ 48,036 Establishment of valuation allowances: Net operating losses 20,805 10,318 82,155 Foreign tax credits 2,877 62,400 — Other deferred tax assets 14,213 4,823 27,928 Releases of valuation allowances in various jurisdictions (79,387 ) (13,472 ) (11,472 ) Valuation allowance as of December 31 $ 169,224 $ 210,716 $ 146,647
Tax Benefits of NOL Carryforwards	Unless utilized, the NOL carryforwards will expire between 2021 and 2037 as follows: Year Expiring Tax Benefit of Carryforwards (In millions) 2021 $ 5.1 2022 0.2 2023 0.1 2025 28.7 2027 7.6 2036 17.9 2037 0.2 Total $ 59.8
Schedule of Foreign Tax Credits	Unless utilized, our excess foreign tax credits of $27.6 million in the U.S. will expire in 2019 and in the years 2024 to 2027 as follows: Year Expiring Foreign Tax (In millions) 2019 $ 0.8 2024 3.1 2025 3.5 2026 20.0 2027 0.2 Total $ 27.6
Summary of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits, Excluding Interest and Penalties	A reconciliation of the beginning and ending amount of unrecognized tax benefits, gross of tax carryforwards and excluding interest and penalties, is as follows: For the Year Ended December 31, 2017 2016 2015 (In thousands) Balance, beginning of period $ (34,970 ) $ (53,952 ) $ (57,116 ) Additions for current year tax positions (51,260 ) (4,233 ) (7,013 ) Additions for prior year tax positions (2,938 ) (1,020 ) (82 ) Reductions for prior year tax positions 623 19,661 2,673 Reductions related to statute of limitation expirations 6,681 4,574 7,586 Balance, end of period $ (81,864 ) $ (34,970 ) $ (53,952 )

Segments and Geographic Area 38

Segments and Geographic Area Analysis (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Revenues from Contract Drilling Services by Equipment Type	Revenues from contract drilling services by equipment-type are listed below: Year Ended December 31, 2017 2016 2015 (In thousands) Floaters: Ultra-Deepwater $ 1,090,139 $ 989,158 $ 1,339,059 Deepwater 202,329 256,997 548,667 Mid-Water 137,607 248,846 387,549 Total Floaters 1,430,075 1,495,001 2,275,275 Jack-ups 21,144 30,213 84,909 Total contract drilling revenues 1,451,219 1,525,214 2,360,184 Revenues related to reimbursable expenses 34,527 75,128 59,209 Total revenues $ 1,485,746 $ 1,600,342 $ 2,419,393
Revenues by Geographic Area Presented by Attributing Revenues to Individual Country	Revenues by geographic area are presented by attributing revenues to the individual country or areas where the services were performed. Year Ended December 31, 2017 2016 2015 (In thousands) United States $ 630,595 $ 548,024 $ 513,605 International: South America 348,479 434,956 812,271 Australia/Asia 307,925 234,182 415,033 Europe 177,603 344,964 532,824 Mexico 21,144 38,216 145,660 855,151 1,052,318 1,905,788 Total revenues $ 1,485,746 $ 1,600,342 $ 2,419,393
Individual Countries that Comprised 5% or More of Our Total Contract Drilling Revenues from Unaffiliated Customers	For the years ended December 31, 2017, 2016 and 2015, individual countries that comprised 5% or more of our total contract drilling revenues from unaffiliated customers are listed below. Year Ended December 31, 2017 2016 2015 Brazil 18.9 % 18.0 % 23.1 % United Kingdom 12.0 % 15.3 % 11.4 % Malaysia 11.2 % 1.7 % 6.8 % Australia 9.5 % 12.8 % 7.0 % Trinidad & Tobago 4.6 % 9.2 % 9.8 % Mexico 1.4 % 2.4 % 6.0 % Romania — 4.0 % 9.7 %
Long-Lived Tangible Assets by Geographic Location	The following table presents our long-lived tangible assets by geographic location as of December 31, 2017, 2016 and 2015. A substantial portion of our assets is comprised of rigs that are mobile, and therefore asset locations at the end of the period are not necessarily indicative of the geographic distribution of the earnings generated by such assets during the periods and may vary from period to period due to the relocation of rigs. In circumstances where our drilling rigs were in transit at the end of a calendar year, they have been presented in the tables below within the geographic area in which they were expected to operate. December 31, 2017 (1) 2016 (1) 2015 (1) (In thousands) Drilling and other property and equipment, net: United States $ 2,300,956 $ 2,753,511 $ 3,292,474 International: Australia/Asia/Middle East 1,714,246 1,429,563 1,224,089 South America 923,398 1,030,069 1,051,283 Europe/Africa 320,473 380,462 664,520 Mexico 2,568 133,330 146,448 2,960,685 2,973,424 3,086,340 Total $ 5,261,641 $ 5,726,935 $ 6,378,814 (1) During 2017, 2016 and 2015, we recorded aggregate impairment losses of $99.3 million, $678.1 million and $860.4 million, respectively, to write down certain of our drilling rigs and related equipment with indicators of impairment to their estimated recoverable amounts.
Countries Where Parent Company had Material Concentration of Operating Assets	The following table presents the countries in which material concentrations of our long-lived tangible assets were located as of December 31, 2017, 2016 and 2015: December 31, 2017 2016 2015 United States 43.7 % 48.1 % 51.6 % Malaysia 20.6 % 13.6 % 10.4 % Brazil 17.5 % 16.8 % 15.3 % Australia 12.0 % 11.4 % 4.5 %
Revenues from Major Customers that Contributed More than 10% of Total Revenues	Revenues from our major customers for the years ended December 31, 2017, 2016 and 2015 that contributed more than 10% of our total revenues are as follows: Year Ended December 31, Customer 2017 2016 2015 Anadarko 24.9 % 22.4 % 12.4 % Petróleo Brasileiro S.A. 18.9 % 17.9 % 24.1 % Hess Corporation 16.0 % 7.7 % 0.3 % BP 15.8 % 9.0 % 0.1 % ExxonMobil — 5.8 % 12.4 %

Unaudited Quarterly Financial39

Unaudited Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Unaudited Quarterly Financial Data	Unaudited summarized financial data by quarter for the years ended December 31, 2017 and 2016 is shown below. First Second Third Fourth (In thousands, except per share data) 2017 Revenues $ 374,226 $ 399,289 $ 366,023 $ 346,208 Operating income (loss) (1) 50,859 20,824 58,581 (6,385 ) Income (loss) before income tax expense 24,462 (7,020 ) (3,801 ) (35,081 ) Net income (loss) 23,539 15,949 10,799 (31,941 ) Net income (loss) per share, basic and diluted $ 0.17 $ 0.12 $ 0.08 $ (0.23 ) 2016 Revenues $ 470,543 $ 388,747 $ 349,178 $ 391,874 Operating income (loss) (2) 111,569 (626,669 ) 54,071 104,145 Income (loss) before income tax expense 83,196 (666,115 ) 34,746 79,874 Net income (loss) 87,425 (589,937 ) 13,927 116,082 Net income (loss) per share, basic and diluted $ 0.64 $ (4.30 ) $ 0.10 $ 0.85 (1) During the second and fourth quarters of 2017, we recognized an aggregate impairment loss of $71.2 million and $28.0 million, respectively, to write down certain of our drilling rigs with indicators of impairment to their estimated recoverable amounts. See Notes 1 and 2. (2) During the second quarter of 2016, we recognized an aggregate impairment loss of $678.1 million to write down certain of our drilling rigs and related spare parts with indicators of impairment to their estimated recoverable amounts. See Notes 1 and 2.

General Information - Additiona

General Information - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Rigsshares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)	Feb. 09, 2018
Property, Plant and Equipment [Line Items]
Number of offshore rigs owned | Rigs	17
Period considered to treat short-term, highly liquid investments as cash equivalents	Three months or less
Amount capitalized for asset replacements and betterments | $	$ 69,400	$ 177,600
Value of shares acquired in satisfaction of tax withholding obligations | $	$ 483	$ 181	$ 236
Initial term of contracts minimum months	2 months
Initial term of contracts maximum months	60 months
Accounting Standards Update 2016-16 [Member]
Property, Plant and Equipment [Line Items]
Reduction in retained earnings | $	$ 18,000
Restricted Stock Units (RSUs) [Member]
Property, Plant and Equipment [Line Items]
Shares acquired in satisfaction of tax withholding obligations | shares	29,416	7,923
Value of shares acquired in satisfaction of tax withholding obligations | $	$ 500	$ 200
Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Outstanding common stock owned by Loews Corporation				53.00%
Assets Held for Sale [Member]
Property, Plant and Equipment [Line Items]
Number of offshore rigs owned | Rigs	2
Carrying values of rigs in disposal group | $	$ 96,300	$ 400
Assets Held for Sale [Member] | Ocean Victory [Member]
Property, Plant and Equipment [Line Items]
Carrying values of rigs in disposal group | $	$ 1,200
Ultra-deepwater Drillship [Member]
Property, Plant and Equipment [Line Items]
Number of offshore rigs owned | Rigs	4
Ultra-Deepwater Rigs [Member]
Property, Plant and Equipment [Line Items]
Number of offshore rigs owned | Rigs	7
Deepwater [Member]
Property, Plant and Equipment [Line Items]
Number of offshore rigs owned | Rigs	4
Mid-Water Floaters [Member]
Property, Plant and Equipment [Line Items]
Number of offshore rigs owned | Rigs	2
Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life for drilling rigs and equipment	3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life for drilling rigs and equipment	30 years

General Information - Reconcili

General Information - Reconciliation of Total Interest Cost to Interest Expense, Net of Amounts Capitalized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Costs Incurred [Abstract]
Total interest cost including amortization of debt issuance costs	$ 113,618	$ 110,748	$ 110,242
Capitalized interest	(90)	(20,814)	(16,308)
Total interest expense as reported	$ 113,528	$ 89,934	$ 93,934

Asset Impairments - Additional

Asset Impairments - Additional Information (Detail) $ in Thousands	3 Months Ended						12 Months Ended
	Dec. 31, 2017USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2017USD ($)Rigs	Dec. 31, 2016USD ($)Rigs	Dec. 31, 2015USD ($)Rigs
Schedule Of Asset Impairment Charges [Line Items]
Impairment of assets | $	$ 28,000	$ 71,200	$ 678,100				$ 99,313	$ 678,145	$ 860,441
2017 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs evaluated for impairment							10
Number of rigs impaired							3
Impaired long-lived assets held and used, method for determining fair value							We estimated the fair value of two of the 2017 Impaired Rigs using an income approach in which the fair value was estimated based on a calculation of the rig’s discounted future net cash flows over its remaining economic life, which utilized significant unobservable inputs, including, but not limited to, assumptions related to estimated dayrate revenue, rig utilization, estimated reactivation and regulatory survey costs, as well as estimated proceeds that may be received on ultimate disposition of the rig. The fair value of the other 2017 Impaired Rig was estimated using a market approach, which required us to estimate the value that would be received for the rig in the principal or most advantageous market for that rig in an orderly transaction between market participants. This estimate was primarily based on an indicative bid to purchase the rig, as well as our evaluation of other market data points; however, the rig has not been sold. Our fair value estimates were representative of Level 3 fair value measurements due to the significant level of estimation involved and the lack of transparency as to the inputs used.
Impairment of assets | $	$ 28,000	$ 71,300					$ 99,300
2016 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs evaluated for impairment								15
Number of rigs impaired								8
Impaired long-lived assets held and used, method for determining fair value							We estimated the fair value of the 2016 Impaired Rigs using an income approach, as described above. Our fair value estimates were representative of Level 3 fair value measurements due to the significant level of estimation involved and the lack of transparency as to the inputs used
Impairment of assets | $			$ 670,000					$ 670,000
2015 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs evaluated for impairment									25
Number of rigs impaired									17
Impaired long-lived assets held and used, method for determining fair value							We estimated the fair value of 16 of the 2015 Impaired Rigs utilizing a market approach, as described above. We estimated the fair value of the one remaining 2015 Impaired Rig using an income approach, as discussed above. Our fair value estimates are representative of Level 3 fair value measurements due to the significant level of estimation involved and the lack of transparency as to the inputs used.
Impairment of assets | $				$ 499,400	$ 2,600	$ 358,500			$ 860,400
Ultra-deep Water Rigs [Member] | 2017 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired							1
Ultra-deep Water Rigs [Member] | 2016 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired								3
Ultra-deep Water Rigs [Member] | 2015 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired									2
Deep Water Rigs [Member] | 2017 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired							1
Deep Water Rigs [Member] | 2016 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired								3
Deep Water Rigs [Member] | 2015 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired									1
Jack-ups [Member] | 2017 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired							1
Jack-ups [Member] | 2015 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired									5
Mid-Water Drilling Rigs [Member] | 2016 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired								3
Mid-Water Drilling Rigs [Member] | 2015 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired									9
Rig with Fair Values Estimated Using Market Approach [Member] | 2015 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Total rigs estimated using market approach									16
Rig with Fair Values Estimated Using Income Approach [Member] | 2015 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Total rigs estimated using income approach									1

Supplemental Financial Inform43

Supplemental Financial Information - Accounts Receivable, Net of Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Trade receivables	$ 247,453	$ 236,040
Value added tax receivables	14,067	14,639
Related party receivables	205	149
Other	464	1,659
Receivables Gross Current, Total	262,189	252,487
Allowance for bad debts	(5,459)	(5,459)	$ (5,724)	$ (5,724)
Total	$ 256,730	$ 247,028

Supplemental Financial Inform44

Supplemental Financial Information - Changes in Provision for Bad Debts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Allowance for bad debts, beginning of year	$ 5,459	$ 5,724	$ 5,724
Bad debt recovery	0	(265)	0
Allowance for bad debts, end of year	$ 5,459	$ 5,459	$ 5,724

Supplemental Financial Inform45

Supplemental Financial Information - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Rig spare parts and supplies	$ 28,383	$ 25,343
Deferred mobilization costs	51,297	61,488
Prepaid BOP Lease	3,873	3,873
Prepaid insurance	3,091	3,771
Prepaid taxes	67,212	2,894
Other	3,769	4,777
Total	$ 157,625	$ 102,146

Supplemental Financial Inform46

Supplemental Financial Information - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Loss on impairment of assets	$ 28,000	$ 71,200	$ 678,100	$ 99,313	$ 678,145	$ 860,441
2017 Reduction Plan [Member]
Condensed Financial Statements, Captions [Line Items]
Accrued costs associated with Corporate Reduction Plan				13,600
2017 Reduction Plan [Member] | Rig Operating Expenses [Member]
Condensed Financial Statements, Captions [Line Items]
Accrued costs associated with Corporate Reduction Plan				11,500
2017 Reduction Plan [Member] | Payroll and Benefits [Member]
Condensed Financial Statements, Captions [Line Items]
Accrued costs associated with Corporate Reduction Plan				$ 2,100
Rig Spare Parts and Supplies [Member]
Condensed Financial Statements, Captions [Line Items]
Loss on impairment of assets					$ 8,100

Supplemental Financial Inform47

Supplemental Financial Information - Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Rig operating expenses	$ 48,894	$ 33,732
Payroll and benefits	46,560	45,619
Deferred revenue	11,371	9,522
Accrued capital project/upgrade costs	3,698	60,308
Interest payable	28,234	18,365
Personal injury and other claims	5,699	6,424
Other	10,199	8,189
Total	$ 154,655	$ 182,159

Supplemental Financial Inform48

Supplemental Financial Information - Noncash Investing and Financing Activities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Accrued but unpaid capital expenditures at period end	$ 3,698	$ 60,308	$ 84,146
Common stock withheld for payroll tax obligations	483	181	236
Cash interest payments	97,096	105,987	110,412
U.S Federal [Member]
Cash income taxes paid (refunded), net:
Cash income taxes paid, net of refunds		(31,151)	(21,751)
Foreign [Member]
Cash income taxes paid (refunded), net:
Cash income taxes paid, net of refunds	43,999	48,931	69,697
State [Member]
Cash income taxes paid (refunded), net:
Cash income taxes paid, net of refunds	$ 94	$ 1	$ 58

Supplemental Financial Inform49

Supplemental Financial Information - Noncash Investing and Financing Activities (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Interest payments, net of amounts capitalized	$ 97	$ 86.1	$ 94.7
Restricted Stock [Member]
Condensed Financial Statements, Captions [Line Items]
Number of shares of common stock withheld	29,416	7,923

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASU, No. 2016-09 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reduction in retained earnings	$ 600,000
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options and SARs, vesting period	4 years
Expiration (in years)	10 years
Weighted-average grant date fair values of awards granted	$ 5.61	$ 9.32	$ 14.44
Intrinsic value of awards exercised	$ 0	$ 0	$ 0
Fair value of awards vested	1,200,000	$ 2,200,000	$ 3,600,000
Time-vesting RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of awards vested	$ 1,100,000
Number of Equity Instruments Awarded in Period	276,085	183,076	153,493
Risk free interest rate used to value non-participating awards			1.48%
Number of Awards, vested	68,659	0	0
Time-vesting RSUs [Member] | Two Years from the Date of Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of RSUs vesting	50.00%
Time-vesting RSUs [Member] | Three Year from the Date of Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of RSUs vesting	50.00%
Performance-Vesting RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of awards vested	$ 300,000	$ 400,000	$ 600,000
Number of Equity Instruments Awarded in Period	370,616	248,188	169,312
Risk free interest rate used to value non-participating awards			1.48%
Number of Awards, vested	18,876
Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost recognized for time-vested awards	$ 8,700,000	$ 7,000,000	$ 5,700,000
Tax benefits recognized	2,600,000	$ 2,400,000	$ 1,900,000
Unrecognized compensation cost related to nonvested awards under the Equity Plan	$ 11,200,000
Expected weighted average period to recognized compensation cost related to nonvested awards under the Equity Plan	2 years
Equity Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock available for issuance	7,500,000

Stock-Based Compensation - Retr

Stock-Based Compensation - Retrospective Effect of Adoption that Impacted on Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Jan. 01, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Retained earnings	$ 1,964,497	$ 1,946,131	$ 1,946,765
Additional paid-in capital	$ 2,011,397	2,005,148	$ 2,004,514
Scenario, Previously Reported [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Retained earnings		1,946,765
Additional paid-in capital		2,004,514
Restatement Adjustment [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Retained earnings		(634)
Additional paid-in capital		$ 634

Stock-Based Compensation - Weig

Stock-Based Compensation - Weighted Average Assumptions Used in Estimating Fair Value of Options and SARs (Detail) - Stock Appreciation Rights (SARs) [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of SARs (in years)	7 years	7 years	6 years
Expected volatility	31.70%	45.79%	55.12%
Dividend yield		0.60%	1.70%
Risk free interest rate	2.09%	1.46%	1.66%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Activity Under Stock Plan (Detail) - Stock Appreciation Rights (SARs) [Member] $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Awards Outstanding, Beginning Balance | shares	1,449,706
Number of Awards, granted | shares	66,000
Number of Awards, exercised | shares	0
Number of Awards, forfeited | shares	5,240
Number of Awards, expired | shares	248,352
Number of Awards, Outstanding, Ending Balance | shares	1,262,114
Number of Awards, exercisable | shares	1,230,382
Weighted-Average Exercise Price Outstanding, Beginning Balance | $ / shares	$ 67.43
Weighted-Average Exercise Price, granted | $ / shares	14.95
Weighted-Average Exercise Price, exercised | $ / shares	0
Weighted-Average Exercise Price, forfeited | $ / shares	41.88
Weighted-Average Exercise Price, expired | $ / shares	90.95
Weighted-Average Exercise Price Outstanding, Ending Balance | $ / shares	60.16
Weighted-Average Exercise Price Outstanding, exercisable | $ / shares	$ 60.63
Weighted-Average Remaining Contractual Term, outstanding	4 years 3 months 19 days
Weighted-Average Remaining Contractual Term, exercisable	4 years 2 months 12 days
Aggregate Intrinsic Value, outstanding | $	$ 272
Aggregate Intrinsic Value, exercisable | $	$ 272

Stock-Based Compensation - Su54

Stock-Based Compensation - Summary of Restricted Stock Units Awarded Under Equity Plan (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Time-vesting RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Awards, Nonvested, Beginning Balance	319,560
Number of Awards, granted	276,085	183,076	153,493
Number of Awards, vested	68,659	0	0
Number of Awards, forfeited	55,697
Number of Awards, Nonvested, Ending Balance	471,289	319,560
Weighted-Average Grant Date Fair Value Per Share, Nonvested, Beginning Balance	$ 23.13
Weighted-Average Grant Date Fair Value Per Share, granted	16.37
Weighted-Average Grant Date Fair Value Per Share, vested	25.08
Weighted-Average Grant Date Fair Value Per Share, forfeited	20.76
Weighted-Average Grant Date Fair Value Per Share, Nonvested, Ending Balance	$ 19.15	$ 23.13
Performance-Vesting RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Awards, Nonvested, Beginning Balance	431,706
Number of Awards, granted	370,616	248,188	169,312
Number of Awards, vested	18,876
Number of Awards, forfeited	55,590
Number of Awards, Nonvested, Ending Balance	727,856	431,706
Weighted-Average Grant Date Fair Value Per Share, Nonvested, Beginning Balance	$ 24.55
Weighted-Average Grant Date Fair Value Per Share, granted	16.61
Weighted-Average Grant Date Fair Value Per Share, vested	46.64
Weighted-Average Grant Date Fair Value Per Share, forfeited	19.95
Weighted-Average Grant Date Fair Value Per Share, Nonvested, Ending Balance	$ 20.28	$ 24.55

Earnings (Loss) Per Share - Rec

Earnings (Loss) Per Share - Reconciliation of Numerators and Denominators of Basic and Diluted Per-Share Computations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income (loss) - basic and diluted (numerator):	$ (31,941)	$ 10,799	$ 15,949	$ 23,539	$ 116,082	$ 13,927	$ (589,937)	$ 87,425	$ 18,346	$ (372,503)	$ (274,285)
Weighted-average shares - basic (denominator):									137,213	137,168	137,157
Dilutive effect of stock-based awards									52
Weighted-average shares including conversions - diluted (denominator):									137,265	137,168	137,157
Earnings (loss) per share:
Basic									$ 0.13	$ (2.72)	$ (2)
Diluted									$ 0.13	$ (2.72)	$ (2)

Earnings (Loss) Per Share - Sec

Earnings (Loss) Per Share - Securities Excluded from Computation of Diluted Earning (Loss) Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Options [Member]
Employee and director:
Securities excluded from computation of diluted earning per share		7	26
Restricted Stock Units (RSUs) [Member]
Employee and director:
Securities excluded from computation of diluted earning per share	757	704	278
Stock Appreciation Rights (SARs) [Member]
Employee and director:
Securities excluded from computation of diluted earning per share	1,315	1,505	1,553

Derivative Financial Instrume57

Derivative Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of foreign currency contracts settled	$ 91,600,000
Derivative contracts outstanding		$ 0	$ 0
Amount of loss recognized	(8,364,000)
Contract Drilling [Member] | FOREX Contracts Designated as Accounting Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss recognized	(8,400,000)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from AOCGL due to the probability of a forecasted transaction not occurring	$ 0

Derivative Financial Instrume58

Derivative Financial Instruments - Amounts Recognized in Consolidated Balance Sheets and Consolidated Statements of Operations Related to Derivative Financial Instruments Designated as Cash Flow Hedges (Detail) - Derivative Designated as Accounting Hedges [Member] - FOREX Contracts [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss recognized in AOCGL on derivative (effective portion)	$ (2,420)
Contract Drilling Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss reclassified from AOCGL into income (effective portion)	(7,829)
Foreign Currency Transaction Gain (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	$ (1)

Financial Instruments and Fai59

Financial Instruments and Fair Value Disclosures - Additional Information (Detail) - USD ($)	Oct. 18, 2016	Oct. 18, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between fair value levels			$ 0	$ 0
Measurement period for determining fair value of debt instruments			10 years
Level 1 [Member] | Cash Held in Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments			$ 337,100,000	125,700,000
Level 1 [Member] | Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments			20,900,000	20,600,000
Niko [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount receivable under settlement agreement			$ 28,000,000		$ 80,000,000
Cash received pursuant to Settlement Agreement		$ 49,000,000
Percentage of future payments of amounts to be retained pursuant to waterfall distribution under credit facility	20.00%
Cash proceeds from legal settlements				$ 3,000,000

Financial Instruments and Fai60

Financial Instruments and Fair Value Disclosures - Assets and Liabilities Measured at Fair Value on Recurring and Nonrecurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets:
Loss on assets	$ 28,000	$ 71,200	$ 678,100	$ 99,313	$ 678,145	$ 860,441
Carrying value of impaired assets	1,000			1,000	45,100
Fair Value Measurements, Recurring [Member]
Assets:
Short-term investments	358,019			358,019	146,360
Mortgage-backed securities					35
Total assets					146,395
Fair Value Measurements, Recurring [Member] | Level 1 [Member]
Assets:
Short-term investments	358,019			358,019	146,360
Total assets					146,360
Fair Value Measurements, Recurring [Member] | Level 2 [Member]
Assets:
Mortgage-backed securities					35
Total assets					35
Nonrecurring Fair Value Measurements [Member]
Assets:
Loss on assets				99,313	678,145
Carrying value of impaired assets	97,261			97,261	69,153
Nonrecurring Fair Value Measurements [Member] | Level 3 [Member]
Assets:
Carrying value of impaired assets	$ 97,261			$ 97,261	$ 69,153

Financial Instruments and Fai61

Financial Instruments and Fair Value Disclosures - Assets and Liabilities Measured at Fair Value on Recurring and Nonrecurring Basis (Parenthetical) (Detail) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2017USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2017USD ($)Rigs	Dec. 31, 2016USD ($)Rigs	Dec. 31, 2015USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment of assets	$ 28,000	$ 71,200	$ 678,100	$ 99,313	$ 678,145	$ 860,441
Carrying value of impaired assets	1,000			1,000	45,100
Book value of physical assets	5,261,641			5,261,641	5,726,935	$ 6,378,814
Rig Spare Parts and Supplies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment of assets					8,100
Carrying value of impaired assets					23,600
Held for Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired assets	96,300			96,300	400
2017 Impaired Rigs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment of assets	28,000	$ 71,300		$ 99,300
Number of rigs written down to their estimated fair value | Rigs				3
2017 Impaired Rigs [Member] | Jack-ups [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of rigs written down to their estimated fair value | Rigs				1
2016 Impaired Rigs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment of assets			$ 670,000		$ 670,000
Number of rigs written down to their estimated fair value | Rigs					8
Nonrecurring Fair Value Measurements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment of assets				$ 99,313	$ 678,145
Carrying value of impaired assets	$ 97,261			$ 97,261	$ 69,153
Nonrecurring Fair Value Measurements [Member] | Drilling Rigs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of rigs written down to their estimated fair value | Rigs					11
Book value of physical assets					$ 45,500
Nonrecurring Fair Value Measurements [Member] | Ultra-Deepwater Rigs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of rigs written down to their estimated fair value | Rigs				1
Nonrecurring Fair Value Measurements [Member] | Deepwater Semisubmersible Rigs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of rigs written down to their estimated fair value | Rigs				1
Nonrecurring Fair Value Measurements [Member] | Jack-ups [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of rigs written down to their estimated fair value | Rigs				1
Prepaid Expenses and Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired assets					$ 23,600

Financial Instruments and Fai62

Financial Instruments and Fair Value Disclosures - Fair Value and Related Carrying Values of Our Debt Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
5.875% Senior Notes due 2019 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		$ 518.6
Carrying Value		499.8
3.45% Senior Notes due 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	$ 223.1	215
Carrying Value	249.4	249.3
7.875% Senior Notes due 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	523.1
Carrying Value	496.5
5.70% Senior Notes due 2039 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	405	392.5
Carrying Value	497.2	497.1
4.875% Senior Notes due 2043 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	547.5	532.7
Carrying Value	$ 748.9	$ 748.9

Financial Instruments and Fai63

Financial Instruments and Fair Value Disclosures - Fair Value and Related Carrying Values of Our Debt Instruments (Parenthetical) (Detail)	Dec. 31, 2017	Dec. 31, 2016
5.875% Senior Notes due 2019 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate of senior notes	5.875%	5.875%
3.45% Senior Notes due 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate of senior notes	3.45%	3.45%
7.875% Senior Notes due 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate of senior notes	7.875%	7.875%
5.70% Senior Notes due 2039 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate of senior notes	5.70%	5.70%
4.875% Senior Notes due 2043 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate of senior notes	4.875%	4.875%

Drilling and Other Property a64

Drilling and Other Property and Equipment - Summary of Cost and Accumulated Depreciation of Drilling and Other Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment	$ 8,177,406	$ 9,087,942
Less accumulated depreciation	(2,855,765)	(3,361,007)
Drilling and other property and equipment, net	5,261,641	5,726,935	$ 6,378,814
Drilling Rigs and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	7,971,406	8,950,385
Land and Buildings [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	63,309	64,449
Office Equipment and Other [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 82,691	$ 73,108

Drilling and Other Property a65

Drilling and Other Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Loss on impairment of assets	$ 28,000	$ 71,200	$ 678,100	$ 99,313	$ 678,145	$ 860,441
2017 Impaired Rigs [Member]
Property, Plant and Equipment [Line Items]
Loss on impairment of assets	$ 28,000	$ 71,300		$ 99,300
2016 Impaired Rigs [Member]
Property, Plant and Equipment [Line Items]
Loss on impairment of assets			$ 670,000		$ 670,000

Credit Agreement and Senior N66

Credit Agreement and Senior Notes - Credit Agreement - Additional Information (Detail) - USD ($)	Oct. 22, 2015	Dec. 31, 2017	Feb. 09, 2018	Dec. 31, 2016
Debt Instrument [Line Items]
Commitment fee on unused commitments		0.20%
Ratio of consolidated indebtedness to total capitalization		60.00%
Borrowings outstanding		$ 0		$ 104,200,000
Borrowings weighted average interest rate				1.90%
Subsequent Event [Member]
Debt Instrument [Line Items]
Amount outstanding under credit agreement			$ 0
Additional amount available under Credit Agreement			1,500,000,000
Borrowings outstanding			$ 0
Eurodollar [Member]
Debt Instrument [Line Items]
Basis point increase		1.00%
Federal Funds Rate [Member]
Debt Instrument [Line Items]
Basis point increase		0.50%
ABR Loans [Member]
Debt Instrument [Line Items]
Interest margin		0.25%
Eurodollar Loans [Member]
Debt Instrument [Line Items]
Interest margin		1.25%
Swingline Loans [Member]
Debt Instrument [Line Items]
Amount available for general purposes	$ 100,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Amount available for general purposes	$ 1,500,000,000
Maturity period of credit agreement	Oct. 22, 2020
Additional amount available under revolving credit facility	$ 500,000,000
Extension of the maturity date under credit agreement		One additional one-year extension of the maturity date
Credit Agreement Commitments Mature on March 17, 2019 [Member]
Debt Instrument [Line Items]
Amount available for general purposes	$ 40,000,000
Maturity period of credit agreement	Mar. 17, 2019
Credit Agreement Commitments Mature on October 22, 2019 [Member]
Debt Instrument [Line Items]
Amount available for general purposes	$ 60,000,000
Maturity period of credit agreement	Oct. 22, 2019
Letters of Credit [Member]
Debt Instrument [Line Items]
Amount available for general purposes	$ 250,000,000
Swingline Loan Facility [Member]
Debt Instrument [Line Items]
Swingline loans bear interest description		Swingline loans bear interest, at our option, at a rate per annum equal to (i) the ABR plus the applicable interest margin for ABR loans or (ii) the daily one-month Eurodollar Rate plus the applicable interest margin for Eurodollar loans
Performance Letters of Credit [Member]
Debt Instrument [Line Items]
Participation fees for letters of credit		0.625%
Other Letter of Credit [Member]
Debt Instrument [Line Items]
Participation fees for letters of credit		1.25%

Credit Agreement and Senior N67

Credit Agreement and Senior Notes - Summary of Senior Notes (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount		$ 250
Maturity date		Nov. 1, 2023
Interest rate Coupon, senior notes		3.45%	3.45%
Interest rate Effective, senior notes		3.50%
Semiannual Interest Payment Dates		May 1 and November 1
7.875% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 500	$ 500
Maturity date	Aug. 15, 2025	Aug. 15, 2025
Interest rate Coupon, senior notes		7.875%	7.875%
Interest rate Effective, senior notes		8.00%
Semiannual Interest Payment Dates		February 15 and August 15
5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount		$ 500
Maturity date		Oct. 15, 2039
Interest rate Coupon, senior notes		5.70%	5.70%
Interest rate Effective, senior notes		5.75%
Semiannual Interest Payment Dates		April 15 and October 15
4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount		$ 750
Maturity date		Nov. 1, 2043
Interest rate Coupon, senior notes		4.875%	4.875%
Interest rate Effective, senior notes		4.89%
Semiannual Interest Payment Dates		May 1 and November 1

Credit Agreement and Senior N68

Credit Agreement and Senior Notes - Summary of Senior Notes (Parenthetical) (Detail)	Dec. 31, 2017	Dec. 31, 2016
3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	3.45%	3.45%
7.875% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	7.875%	7.875%
5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	5.70%	5.70%
4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	4.875%	4.875%

Credit Agreement and Senior N69

Credit Agreement and Senior Notes - Summary of Carrying Value of Senior Notes, Net of Unamortized Discount and Debt Issuance Costs (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Senior Notes	$ 1,972,225	$ 1,980,884
5.875% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Senior Notes		498,679
3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Senior Notes	248,162	247,879
7.875% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Senior Notes	489,420
5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Senior Notes	492,971	492,812
4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Senior Notes	$ 741,672	$ 741,514

Credit Agreement and Senior N70

Credit Agreement and Senior Notes - Summary of Carrying Value of Senior Notes, Net of Unamortized Discount and Debt Issuance Costs (Parenthetical) (Detail)	Dec. 31, 2017	Dec. 31, 2016
5.875% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	5.875%	5.875%
3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	3.45%	3.45%
7.875% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	7.875%	7.875%
5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	5.70%	5.70%
4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	4.875%	4.875%

Credit Agreement and Senior N71

Credit Agreement and Senior Notes - Senior Notes - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Unamortized discounts, net		$ 8,100
Debt issuance costs, net		19,700
Loss on extinguishment of senior notes		35,366
Proceeds from issuance of senior notes		496,360
3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of senior unsecured notes		$ 250,000
Maturity date		Nov. 1, 2023
3.45% Senior Notes due 2023 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes		15 days
3.45% Senior Notes due 2023 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes		60 days
4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of senior unsecured notes		$ 750,000
Maturity date		Nov. 1, 2043
4.875% Senior Notes due 2043 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes		15 days
4.875% Senior Notes due 2043 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes		60 days
7.875% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of senior unsecured notes	$ 500,000	$ 500,000
Proceeds from issuance of senior notes	$ 489,100
Maturity date	Aug. 15, 2025	Aug. 15, 2025
7.875% Senior Notes due 2025 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes		15 days
7.875% Senior Notes due 2025 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes		60 days
5.875% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Redemption of outstanding senior notes	$ 543,000
Loss on extinguishment of senior notes		$ 35,400
5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of senior unsecured notes		$ 500,000
Maturity date		Oct. 15, 2039
5.70% Senior Notes due 2039 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes		15 days
5.70% Senior Notes due 2039 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes		60 days

Credit Agreement and Senior N72

Credit Agreement and Senior Notes - Aggregate Maturities of Senior Notes, Excluding Net Unamortized Discounts and Debt Issuance Costs (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
2,018	$ 0
2,019	0
2,020	0
2,021	0
2,022	0
Thereafter	2,000,000
Total maturities of senior notes	$ 2,000,000

Other Comprehensive Income (L73

Other Comprehensive Income (Loss) - Components of Other Comprehensive Gain (Loss) and Related Income Tax Effects (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 1	$ (5,035)	$ (3,605)
Change in other comprehensive loss before reclassifications		(6,559)	(6,514)
Reclassification adjustments for items included in Net Income (Loss)	(6)	11,595	5,084
Total other comprehensive (loss) gain	(6)	5,036	(1,430)
Ending balance	(5)	1	(5,035)
Derivative Financial Instrument [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1	6	(3,504)
Change in other comprehensive loss before reclassifications			(1,574)
Reclassification adjustments for items included in Net Income (Loss)	(6)	(5)	5,084
Total other comprehensive (loss) gain	(6)	(5)	3,510
Ending balance	$ (5)	1	6
Marketable Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(5,041)	(101)
Change in other comprehensive loss before reclassifications		(6,559)	(4,940)
Reclassification adjustments for items included in Net Income (Loss)		11,600
Total other comprehensive (loss) gain		$ 5,041	(4,940)
Ending balance			$ (5,041)

Other Comprehensive Income (L74

Other Comprehensive Income (Loss) - Components of Other Comprehensive Gain (Loss) and Related Income Tax Effects (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Change in other comprehensive loss on derivatives, tax expense (benefit)		$ 0	$ 846
Change in other comprehensive loss on marketable securities, tax (expense) benefit		2	(1)
Reclassification adjustments for items included in Net Income (Loss) on derivatives, tax (expense) benefit	$ 2	3	(2,737)
Reclassification adjustments for items included in Net Income (Loss) on marketable securities, tax (expense) benefit	$ 0	$ 0	$ 0

Other Comprehensive Income (L75

Other Comprehensive Income (Loss) - Items in Consolidated Statements of Operations Affected by Reclassification Adjustments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other, net									$ 2,230	$ (10,727)	$ 873
Contract drilling, excluding depreciation									(801,964)	(772,173)	(1,227,864)
Interest expense									(113,528)	(89,934)	(93,934)
Income tax expense (benefit)									39,786	95,796	107,063
Net income (loss)	$ (31,941)	$ 10,799	$ 15,949	$ 23,539	$ 116,082	$ 13,927	$ (589,937)	$ 87,425	18,346	(372,503)	(274,285)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)									2	3	(2,737)
Net income (loss)									(6)	(5)	5,084
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedges [Member] | FOREX Contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Contract drilling, excluding depreciation											7,829
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedges [Member] | Treasury Lock Agreements [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense									$ (8)	(8)	$ (8)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Marketable Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other, net										11,600
Net income (loss)										$ 11,600

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Feb. 29, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 12, 2017
Contingencies And Commitments [Line Items]
Deductible for marine liability coverage including personal injury claims, per first occurrence		$ 10,000,000
Range of deductible for liability coverage for personal injury claims, lower limit		5,000,000
Range of deductible for liability coverage for personal injury claims, upper limit		100,000,000
Purchase obligations		0
Rental expense under operating leases		3,900,000	$ 5,500,000	$ 7,800,000
Future minimum rental payments under leases, in current years		1,700,000
Future minimum rental payments under leases, in two years		500,000
Future minimum rental payments under leases, in three years		300,000
Future minimum rental payments under leases, in four years		300,000
Future minimum rental payments under leases, in five years		$ 300,000
Maturity of lease agreement	10 years	10 years	10 years
Total Contingent Liabilities Under Letters of Credit and Bonds [Member]
Contingencies And Commitments [Line Items]
Contingent liability under letters of credit and other bonds		$ 20,400,000
Potentially Collateralized Contingent Liability Under Letters Of Credit and Bonds [Member]
Contingencies And Commitments [Line Items]
Contingent liability under letters of credit and other bonds		14,800,000
Windstorms in U.S. Gulf of Mexico [Member]
Contingencies And Commitments [Line Items]
Deductible for marine liability coverage including personal injury claims, per first occurrence		25,000,000
Range of deductible for liability coverage for personal injury claims, lower limit		25,000,000
Range of deductible for liability coverage for personal injury claims, upper limit		$ 100,000,000
Personal Injury Claims [Member]
Contingencies And Commitments [Line Items]
Personal injury claims recorded			$ 32,900,000		$ 30,900,000
Personal Injury Claims [Member] | Accrued Liabilities [Member]
Contingencies And Commitments [Line Items]
Personal injury claims recorded			6,100,000		5,200,000
Personal Injury Claims [Member] | Other Liabilities [Member]
Contingencies And Commitments [Line Items]
Personal injury claims recorded			$ 26,800,000		$ 25,700,000

Sale and Leaseback Transactio77

Sale and Leaseback Transactions - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 29, 2016Drillship	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)Transactions
Leases [Abstract]
Maturity of lease agreement	10 years	10 years	10 years
Number of new build drillships in lease agreement | Drillship	4
Number of sale and leaseback transactions completed | Transactions			4
Future minimum rental payments under leases			$ 550
Proceeds from sale of equipment			210
Future minimum rental payments under leases per annum			65
Leases and contractual services agreement		$ 61.7	$ 34

Related-Party Transactions - Ad

Related-Party Transactions - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Terms and conditions of service agreement with Loews	The Services Agreement may be terminated at our option upon 30 days’ notice to Loews and at the option of Loews upon six months’ notice to us.
Services Agreement with Loews [Member]
Related Party Transaction [Line Items]
Related party transaction expenses	$ 1,000,000	$ 1,000,000	$ 1,300,000
SEACOR Holdings Inc [Member]
Related Party Transaction [Line Items]
Related party transaction expenses	$ 47,000	$ 700,000	$ 6,000,000

Restructuring and Separation 79

Restructuring and Separation Costs - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring and employee separation related costs	$ 14,146	$ 9,778
2017 Reduction Plan [Member]
Restructuring Cost and Reserve [Line Items]
Accrued costs associated with Corporate Reduction Plan	$ 13,600
Restructuring a cost description	Accrued costs associated with the 2017 Reduction Plan were $13.6 million as of December 31, 2017, of which $11.5 million is related to the termination of our Brazilian agency agreement, which is expected to be paid in the first quarter of 2018, and $2.1 million is related to severance payments to two former executives, payable over a two year period.
2017 Reduction Plan [Member] | Termination of Brazilian Agency Agreement [Member]
Restructuring Cost and Reserve [Line Items]
Accrued costs associated with Corporate Reduction Plan	$ 11,500
2017 Reduction Plan [Member] | Severance Payments [Member]
Restructuring Cost and Reserve [Line Items]
Accrued costs associated with Corporate Reduction Plan	$ 2,100

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
U.S corporate income tax rate			35.00%
Net tax expense related to change in tax rate	$ 1,100
Net operating loss carryforwards, or NOLs	133,298		$ 133,298	$ 159,653
Deferred tax asset relates to NOL carryforwards	73,500		73,500
Net operating loss carryforwards to expire	59,800		59,800
Valuation allowance	110,900		110,900
Deferred tax assets for foreign tax credits	27,623		27,623	95,145
Valuation allowances for other deferred tax assets	31,600		31,600
Addition to current year tax positions			51,260	4,233	$ 7,013
Net increase (decrease) in penalties related to uncertain tax positions from prior years			(623)	(19,661)	(2,673)
Net liability for uncertain tax positions	81,864		81,864	34,970	53,952	$ 57,116
Net unrecognized tax benefits that would affect the effective tax rate	101,900		101,900	36,000	49,400
Accrued interest on uncertain tax positions	3,100		3,100	2,700
Accrued penalties on uncertain tax positions	15,100		15,100	16,800
Interest expense (benefit) recognized related to uncertain tax positions			500	(100)	(4,800)
Penalties recognized related to uncertain tax positions			(1,700)	(23,200)	$ 2,300
Devaluation Of Egyptian Pound [Member]
Income Tax Contingency [Line Items]
Net increase (decrease) in penalties related to uncertain tax positions from prior years				(19,700)
Foreign [Member]
Income Tax Contingency [Line Items]
Charge relating to previously deferred earnings of certain non-US subsidiaries	75,400		75,400
Net operating loss carryforwards, or NOLs	115,200		115,200
Valuation allowance	26,700		26,700
U.S Federal [Member]
Income Tax Contingency [Line Items]
Tax credit resulting from remeasurement of net U.S. deferred tax liabilities	74,300		74,300
Net operating loss carryforwards, or NOLs	18,100		18,100
Scenario, Forecast [Member]
Income Tax Contingency [Line Items]
U.S corporate income tax rate		21.00%
United States [Member]
Income Tax Contingency [Line Items]
Deferred tax assets for foreign tax credits	27,600		27,600
United States [Member] | Foreign Tax Credit Carryforwards [Member]
Income Tax Contingency [Line Items]
Deferred tax assets for foreign tax credits	27,600		$ 27,600
Foreign tax credits expiration periods			2019 and in the years 2024 to 2027
Mexico [Member] | 2012 Tax Year [Member]
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefit	1,500		$ 1,500
Other Assets [Member]
Income Tax Contingency [Line Items]
Net liability for uncertain tax positions	2,300		2,300	2,100
Deferred Tax Liability [Member]
Income Tax Contingency [Line Items]
Net liability for uncertain tax positions	51,300		51,300	3,100
Other Liabilities [Member]
Income Tax Contingency [Line Items]
Net liability for uncertain tax positions	$ 52,900		$ 52,900	$ 35,000

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal - current	$ 6,994	$ 230	$ 63,223
State - current	95	(60)	93
Foreign - current	25,252	10,297	71,655
Total current	32,341	10,467	134,971
Federal - deferred	(85,066)	(108,274)	(245,045)
Foreign - deferred	12,939	2,011	3,011
Total deferred	(72,127)	(106,263)	(242,034)
Income tax benefit	$ (39,786)	$ (95,796)	$ (107,063)

Income Taxes - Difference Betwe

Income Taxes - Difference Between Actual Income Tax Expense and Tax Provision Computed by Applying Statutory Federal Income Tax Rate to Income Before Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income before income tax expense:
U.S.	$ (241,178)	$ (146,037)	$ (11,158)
Foreign	219,738	(322,262)	(370,190)
Worldwide	(21,440)	(468,299)	(381,348)
Expected income tax benefit at federal statutory rate	(7,504)	(163,905)	(133,472)
Effect of tax rate changes	(74,294)
Mandatory repatriation of earnings pursuant to Tax Reform and Jobs Act	94,194
Effect of foreign operations	(42,102)	48,573	(4,906)
Amortization of deferred charges associated with intercompany rig sales to other tax jurisdictions			38,466
Valuation allowance	(41,492)	62,400
Uncertain tax positions, settlements and adjustments relating to prior years	31,726	(34,666)	(1,114)
Other	(314)	(8,198)	(6,037)
Income tax benefit	$ (39,786)	$ (95,796)	$ (107,063)

Income Taxes - Components of De

Income Taxes - Components of Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards, or NOLs	$ 133,298	$ 159,653
Foreign tax credits	27,623	95,145
Worker's compensation and other current accruals	10,330	14,824
Bareboat charter deductions		23,353
UK depreciation deduction	52,800	21,222
Anticipatory deductions and credits	13,111
Deferred compensation	3,711	4,689
Foreign contribution taxes	3,806	3,857
Stock compensation awards	6,872	11,679
Deferred deductions	94	8,185
Other	3,748	2,526
Total deferred tax assets	255,393	345,133
Valuation allowance	(169,224)	(210,716)	$ (146,647)	$ (48,036)
Net deferred tax assets	86,169	134,417
Deferred tax liabilities:
Property, plant and equipment	(236,038)	(284,480)
Mobilization	(17,192)	(46,274)
Other	(238)	(674)
Total deferred tax liabilities	(253,468)	(331,428)
Net deferred tax liability	$ (167,299)	$ (197,011)

Income Taxes - Summary of Chang

Income Taxes - Summary of Changes in Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance [Line Items]
Valuation allowance as of January 1	$ 210,716	$ 146,647	$ 48,036
Valuation allowance as of December 31	169,224	210,716	146,647
Foreign Tax Credits [Member]
Valuation Allowance [Line Items]
Change in valuation allowance	2,877	62,400
Net Operating Losses [Member]
Valuation Allowance [Line Items]
Change in valuation allowance	20,805	10,318	82,155
Releases of Valuation Allowances in Various Jurisdictions [Member]
Valuation Allowance [Line Items]
Change in valuation allowance	(79,387)	(13,472)	(11,472)
Other Deferred Tax Assets [Member]
Valuation Allowance [Line Items]
Change in valuation allowance	$ 14,213	$ 4,823	$ 27,928

Income Taxes - Tax Benefits of

Income Taxes - Tax Benefits of NOL Carryforwards (Detail) $ in Millions	Dec. 31, 2017USD ($)
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, or NOLs	$ 59.8
2021 [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, or NOLs	5.1
2022 [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, or NOLs	0.2
2023 [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, or NOLs	0.1
2025 [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, or NOLs	28.7
2027 [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, or NOLs	7.6
2036 [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, or NOLs	17.9
2037 [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, or NOLs	$ 0.2

Income Taxes - Schedule of Fore

Income Taxes - Schedule of Foreign Tax Credits (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Tax Credit Carryforward [Line Items]
Foreign Tax Credits, Total	$ 27,623	$ 95,145
2019 [Member]
Tax Credit Carryforward [Line Items]
Foreign Tax Credits, Total	800
2024 [Member]
Tax Credit Carryforward [Line Items]
Foreign Tax Credits, Total	3,100
2025 [Member]
Tax Credit Carryforward [Line Items]
Foreign Tax Credits, Total	3,500
2026 [Member]
Tax Credit Carryforward [Line Items]
Foreign Tax Credits, Total	20,000
2027 [Member]
Tax Credit Carryforward [Line Items]
Foreign Tax Credits, Total	200
United States [Member]
Tax Credit Carryforward [Line Items]
Foreign Tax Credits, Total	27,600
United States [Member] | Foreign Tax Credit Carryforwards [Member]
Tax Credit Carryforward [Line Items]
Foreign Tax Credits, Total	$ 27,600

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits, Excluding Interest and Penalties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance, beginning of period	$ (34,970)	$ (53,952)	$ (57,116)
Additions for current year tax positions	(51,260)	(4,233)	(7,013)
Additions for prior year tax positions	(2,938)	(1,020)	(82)
Reductions for prior year tax positions	623	19,661	2,673
Reductions related to statute of limitation expirations	6,681	4,574	7,586
Balance, end of period	$ (81,864)	$ (34,970)	$ (53,952)

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($)	4 Months Ended	6 Months Ended		12 Months Ended
	Apr. 30, 2015	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Provision for contributions to the Supplemental Plan				$ 136,000	$ 146,000	$ 153,000
US Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, employer profit sharing contribution percent	4.00%
Vesting period for the profit sharing contribution				3 years
Defined contribution plan, cost recognized				$ 8,900,000	$ 12,900,000	$ 23,800,000
Defined Contribution Plan, Matching Contribution per employee by the company				5.00%	6.00%	6.00%
UK Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized				$ 1,400,000	$ 2,000,000	$ 3,400,000
UK Plan [Member] | U. K. Sector of North Sea [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Matching Contribution by the company		6.00%	10.00%	6.00%	10.00%	10.00%
International Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, employer profit sharing contribution percent	4.00%
Defined contribution plan, cost recognized				$ 400,000	$ 800,000	$ 2,200,000
Defined Contribution Plan, Matching Contribution per employee by the company				5.00%	6.00%	6.00%

Segments and Geographic Area 89

Segments and Geographic Area Analysis - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017CountrySegment	Dec. 31, 2016Country	Dec. 31, 2015Country
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	1
Number of countries with rigs	4
Geographic Concentration Risk [Member] | Contract Drilling Revenues [Member]
Segment Reporting Information [Line Items]
Concentration risk benchmark	Individual international country may, from time to time, comprise a material percentage of our total contract drilling revenues
Concentration risk percentage	5.00%	5.00%	5.00%
Geographic Concentration Risk [Member] | Long-lived Tangible Assets [Member]
Segment Reporting Information [Line Items]
Concentration risk benchmark	No other countries had more than a 5% concentration
Concentration risk percentage	5.00%	5.00%	5.00%
Number of other Countries	0	0	0
Customer Concentration Risk [Member] | Revenues [Member]
Segment Reporting Information [Line Items]
Concentration risk benchmark	Contributed more than 10% of our total revenues
Concentration risk percentage	10.00%	10.00%	10.00%

Segments and Geographic Area 90

Segments and Geographic Area Analysis - Revenues from Contract Drilling Services by Equipment Type (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Contract drilling									$ 1,451,219	$ 1,525,214	$ 2,360,184
Revenues related to reimbursable expenses									34,527	75,128	59,209
Total revenues	$ 346,208	$ 366,023	$ 399,289	$ 374,226	$ 391,874	$ 349,178	$ 388,747	$ 470,543	1,485,746	1,600,342	2,419,393
Ultra-Deepwater Rigs [Member]
Segment Reporting Information [Line Items]
Contract drilling									1,090,139	989,158	1,339,059
Deepwater [Member]
Segment Reporting Information [Line Items]
Contract drilling									202,329	256,997	548,667
Mid-Water [Member]
Segment Reporting Information [Line Items]
Contract drilling									137,607	248,846	387,549
Total Floaters [Member]
Segment Reporting Information [Line Items]
Contract drilling									1,430,075	1,495,001	2,275,275
Jack-ups [Member]
Segment Reporting Information [Line Items]
Contract drilling									$ 21,144	$ 30,213	$ 84,909

Segments and Geographic Area 91

Segments and Geographic Area Analysis - Revenues by Geographic Area Presented by Attributing Revenues to Individual Country (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 346,208	$ 366,023	$ 399,289	$ 374,226	$ 391,874	$ 349,178	$ 388,747	$ 470,543	$ 1,485,746	$ 1,600,342	$ 2,419,393
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									630,595	548,024	513,605
South America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									348,479	434,956	812,271
Australia/Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									307,925	234,182	415,033
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									177,603	344,964	532,824
Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									21,144	38,216	145,660
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									$ 855,151	$ 1,052,318	$ 1,905,788

Segment and Geographical Area A

Segment and Geographical Area Analysis - Individual Countries that Comprised 5% or More of Our Total Contract Drilling Revenues from Unaffiliated Customers (Detail) - Revenues [Member] - Geographic Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Brazil Tax Jurisdiction [Member]
Segment Reporting Information [Line Items]
Percentage of total drilling revenues from unaffiliated customers	18.90%	18.00%	23.10%
United Kingdom [Member]
Segment Reporting Information [Line Items]
Percentage of total drilling revenues from unaffiliated customers	12.00%	15.30%	11.40%
Malaysia Tax Jurisdiction [Member]
Segment Reporting Information [Line Items]
Percentage of total drilling revenues from unaffiliated customers	11.20%	1.70%	6.80%
Australia [Member]
Segment Reporting Information [Line Items]
Percentage of total drilling revenues from unaffiliated customers	9.50%	12.80%	7.00%
Trinidad & Tobago [Member]
Segment Reporting Information [Line Items]
Percentage of total drilling revenues from unaffiliated customers	4.60%	9.20%	9.80%
Mexico [Member]
Segment Reporting Information [Line Items]
Percentage of total drilling revenues from unaffiliated customers	1.40%	2.40%	6.00%
Romania [Member]
Segment Reporting Information [Line Items]
Percentage of total drilling revenues from unaffiliated customers		4.00%	9.70%

Segments and Geographic Area 93

Segments and Geographic Area Analysis - Long-Lived Tangible Assets by Geographic Location (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling and other property and equipment, net	$ 5,261,641	$ 5,726,935	$ 6,378,814
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling and other property and equipment, net	2,300,956	2,753,511	3,292,474
Australia/Asia/Middle East [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling and other property and equipment, net	1,714,246	1,429,563	1,224,089
South America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling and other property and equipment, net	923,398	1,030,069	1,051,283
Europe/Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling and other property and equipment, net	320,473	380,462	664,520
Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling and other property and equipment, net	2,568	133,330	146,448
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling and other property and equipment, net	$ 2,960,685	$ 2,973,424	$ 3,086,340

Segments and Geographic Area 94

Segments and Geographic Area Analysis - Long-Lived Tangible Assets by Geographic Location (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting [Abstract]
Impairment of assets	$ 28,000	$ 71,200	$ 678,100	$ 99,313	$ 678,145	$ 860,441

Segments and Geographic Area 95

Segments and Geographic Area Analysis - Countries Where Parent Company had Material Concentration of Operating Assets (Detail) - Geographic Concentration Risk [Member] - Long-lived Tangible Assets [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Entity Wide Disclosure On Geographic Areas Countries Where Parent Company Had Material Concentration Of Operating Assets [Line Items]
Percentage of material concentration of long-lived tangible assets	5.00%	5.00%	5.00%
United States [Member]
Entity Wide Disclosure On Geographic Areas Countries Where Parent Company Had Material Concentration Of Operating Assets [Line Items]
Percentage of material concentration of long-lived tangible assets	43.70%	48.10%	51.60%
Malaysia Tax Jurisdiction [Member]
Entity Wide Disclosure On Geographic Areas Countries Where Parent Company Had Material Concentration Of Operating Assets [Line Items]
Percentage of material concentration of long-lived tangible assets	20.60%	13.60%	10.40%
Brazil Tax Jurisdiction [Member]
Entity Wide Disclosure On Geographic Areas Countries Where Parent Company Had Material Concentration Of Operating Assets [Line Items]
Percentage of material concentration of long-lived tangible assets	17.50%	16.80%	15.30%
Australia [Member]
Entity Wide Disclosure On Geographic Areas Countries Where Parent Company Had Material Concentration Of Operating Assets [Line Items]
Percentage of material concentration of long-lived tangible assets	12.00%	11.40%	4.50%

Segments and Geographic Area 96

Segments and Geographic Area Analysis - Revenues from Major Customers that Contributed More than 10% of Total Revenues (Detail) - Revenues [Member] - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Major Customer [Line Items]
Percentage of revenues from major customers	10.00%	10.00%	10.00%
Anadarko [Member]
Revenue, Major Customer [Line Items]
Percentage of revenues from major customers	24.90%	22.40%	12.40%
Petrobras Brasileiro S.A. [Member]
Revenue, Major Customer [Line Items]
Percentage of revenues from major customers	18.90%	17.90%	24.10%
Hess Corporation [Member]
Revenue, Major Customer [Line Items]
Percentage of revenues from major customers	16.00%	7.70%	0.30%
BP [Member]
Revenue, Major Customer [Line Items]
Percentage of revenues from major customers	15.80%	9.00%	0.10%
ExxonMobil [Member]
Revenue, Major Customer [Line Items]
Percentage of revenues from major customers		5.80%	12.40%

Unaudited Quarterly Financial97

Unaudited Quarterly Financial Data - Unaudited Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Information [Abstract]
Revenues	$ 346,208	$ 366,023	$ 399,289	$ 374,226	$ 391,874	$ 349,178	$ 388,747	$ 470,543	$ 1,485,746	$ 1,600,342	$ 2,419,393
Operating income (loss)	(6,385)	58,581	20,824	50,859	104,145	54,071	(626,669)	111,569	123,879	(356,884)	(294,074)
Income (loss) before income tax expense	(35,081)	(3,801)	(7,020)	24,462	79,874	34,746	(666,115)	83,196	(21,440)	(468,299)	(381,348)
Net income (loss)	$ (31,941)	$ 10,799	$ 15,949	$ 23,539	$ 116,082	$ 13,927	$ (589,937)	$ 87,425	$ 18,346	$ (372,503)	$ (274,285)
Net income (loss) per share, basic and diluted	$ (0.23)	$ 0.08	$ 0.12	$ 0.17	$ 0.85	$ 0.10	$ (4.30)	$ 0.64

Unaudited Quarterly Financial98

Unaudited Quarterly Financial Data - Unaudited Quarterly Financial Data (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Information [Abstract]
Impairment of assets	$ 28,000	$ 71,200	$ 678,100	$ 99,313	$ 678,145	$ 860,441