Shell Midstream Partners (SHLX) 10-Q 2 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 02, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Trading Symbol	SHLX
Entity Registrant Name	Shell Midstream Partners, L.P.
Entity Central Index Key	1,610,466
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		223,811,781

UNAUDITED CONDENSED CONSOLIDATE

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 174.9	$ 137.7
Accounts receivable – third parties, net	19.8	17.2
Accounts receivable – related parties	24.8	23.8
Allowance oil	18.9	12.4
Prepaid expenses	5.2	12.5
Total current assets	243.6	203.6
Equity method investments	820.9	362.6
Property, plant and equipment, net	741.2	736.5
Cost investments	62.1	62.1
Other assets – related parties	2.6	1.7
Total assets	1,870.4	1,366.5
Current liabilities
Accounts payable – third parties	4.4	4
Accounts payable – related parties	12.6	11.6
Deferred revenue – third parties	4.8	5.5
Deferred revenue – related party	6.7	13.9
Accrued liabilities – third parties	26.5	12.7
Accrued liabilities – related parties	11.5	7.2
Total current liabilities	66.5	54.9
Noncurrent liabilities
Debt payable – related party	2,091.5	1,844
Lease liability	23.9	24.3
Asset retirement obligations	6.7	6.6
Other unearned income	2.6	2.6
Total noncurrent liabilities	2,124.7	1,877.5
Total liabilities	2,191.2	1,932.4
Commitments and Contingencies (Note 12)
EQUITY (DEFICIT)
Total partners’ capital	(343.3)	(589.2)
Noncontrolling interests	22.5	23.3
Total deficit	(320.8)	(565.9)
Total liabilities and deficit	1,870.4	1,366.5
Shell Pipeline Company L P
EQUITY (DEFICIT)
General partner unitholders	(3,558.2)	(2,855.5)
Common Units | General Public
EQUITY (DEFICIT)
Common unitholders	3,433.9	2,773.5
Common Units | Shell Pipeline Company L P
EQUITY (DEFICIT)
Common unitholders	$ (219)	$ (507.2)

UNAUDITED CONDENSED CONSOLIDAT3

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Jun. 30, 2018	Dec. 31, 2017
Common unitholders' capital account, units outstanding (in shares)	223,811,781
Shell Pipeline Company L P
General partners' capital account, units issued (in shares)	4,567,588	3,832,293
General partners' capital account, units outstanding (in shares)	4,567,588	3,832,293
Common Units | General Public
Common unitholders' capital account, units issued (in shares)	123,832,233	98,832,233
Common unitholders' capital account, units outstanding (in shares)	123,832,233	98,832,233
Common Units | Shell Pipeline Company L P
Common unitholders' capital account, units issued (in shares)	99,979,548	88,950,136
Common unitholders' capital account, units outstanding (in shares)	99,979,548	88,950,136

UNAUDITED CONDENSED CONSOLIDAT4

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Revenue
Revenue from contract with customer	$ 115.2			$ 201
Lease revenue – related parties	14.1	$ 13.2	[1]	27.9	$ 18.7	[1]
Total revenue	129.3	112.4	[1]	228.9	221.5	[1]
Costs and expenses
Operations and maintenance – third parties	24.9	26.5	[1]	68	45.5	[1]
Operations and maintenance – related parties	13.3	10	[1]	26.7	23.7	[1]
Cost of product sold – third parties	1.2	0		1.2	0
Cost of product sold – related parties	1.2	0	[1]	7.7	0	[1]
General and administrative – third parties	2.2	3.7	[1]	4.1	5.7	[1]
General and administrative – related parties	13.9	11.6	[1]	26.8	23.7	[1]
Depreciation, amortization and accretion	11.4	11.3	[1],[2]	22.8	22.6	[1],[2]
Property and other taxes	4.5	4.2	[1]	10	9.1	[1]
Total costs and expenses	72.6	67.3	[1]	167.3	130.3	[1]
Operating income	56.7	45.1	[1]	61.6	91.2	[1]
Income from equity method investments	48.4	44.7	[1]	88.6	91.4	[1]
Dividend income from cost investments	12.8	9.4	[1]	37.7	19.5	[1]
Other income	10.9	0	[1]	16.3	0	[1]
Investment, dividend and other income	72.1	54.1	[1]	142.6	110.9	[1]
Interest expense, net	13.3	7.5	[1]	23.9	12.3	[1]
Income before income taxes	115.5	91.7	[1]	180.3	189.8	[1]
Income tax expense	0.1	0	[1]	0.1	0	[1]
Net income	115.4	91.7	[1]	180.2	189.8	[1],[2]
Less: Net income attributable to Parent	0	21.5	[1]	0	44	[1]
Less: Net income attributable to noncontrolling interests	4.7	4.7	[1]	5.5	9.5	[1]
Net income attributable to the Partnership	110.7	65.5	[1]	174.7	136.3	[1]
Limited Partners' interest in net income attributable to the Partnership	$ 79.1	$ 51.2	[1]	$ 116.1	$ 109.9	[1]
Net income per Limited Partner Unit - Basic and Diluted
Distributions per Limited Partner unit (in dollars per share)	$ 0.365	$ 0.30410	[1]	$ 0.713	$ 0.5951	[1]
Shell Pipeline Company L P
Costs and expenses
General partner's interest in net income attributable to the Partnership	$ 31.6	$ 14.3	[1]	$ 58.6	$ 26.4	[1]
Common
Costs and expenses
Net income attributable to the Partnership	$ 79.1	$ 51.2		$ 116.1	$ 109.9
Net income per Limited Partner Unit - Basic and Diluted
Net income per Limited Partner unit (in dollars per share)	$ 0.35	$ 0.29	[1]	$ 0.54	$ 0.62	[1]
Common units – public
Costs and expenses
Net income				$ 64.5
Weighted average Limited Partner Units outstanding - Basic and Diluted (in millions)
Weighted average Limited Partner units outstanding - Common (in shares)	123.8	88.4	[1]	118.9	88.4	[1]
Common units – public | Shell Pipeline Company L P
Costs and expenses
Net income				$ 51.6
Common units – SPLC | Shell Pipeline Company L P
Weighted average Limited Partner Units outstanding - Basic and Diluted (in millions)
Weighted average Limited Partner units outstanding - Common (in shares)	100	89	[1]	97.8	88.9	[1]
Product Revenue
Revenue
Revenue from contract with customer	$ 3.1			$ 11
Third Parties | Transportation, Terminaling and Storage Services
Revenue
Revenue from contract with customer	57	$ 59.7	[1]	91.6	$ 118.9	[1]
Third Parties | Product Revenue
Revenue
Revenue from contract with customer	1.4	0	[1]	1.4	0	[1]
Related Parties | Transportation, Terminaling and Storage Services
Revenue
Revenue from contract with customer	55.1	39.5	[1]	98.4	83.9	[1]
Related Parties | Product Revenue
Revenue
Revenue from contract with customer	$ 1.7	$ 0	[1]	9.6	$ 0	[1]
Noncontrolling Interests
Costs and expenses
Net income				$ 5.5
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.
[2]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

UNAUDITED CONDENSED CONSOLIDAT5

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net income		$ 180.2	$ 189.8	[1],[2]
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, amortization and accretion		22.8	22.6	[1],[2]
Non-cash interest expense		0.4	0.1	[2]
Allowance oil reduction to net realizable value		0	0.3	[2]
Undistributed equity earnings		(2.2)	(4.2)	[2]
Changes in operating assets and liabilities
Accounts receivable		(3.5)	(14.5)	[2]
Allowance oil		(6.5)	0.7	[2]
Prepaid expenses and other assets		6.4	1.9	[2]
Accounts payable		1.3	4.6	[2]
Deferred revenue and other unearned income		(3.3)	10.4	[2]
Accrued liabilities		17.6	8.4	[2]
Net cash provided by operating activities		213.2	220.1	[2]
Cash flows from investing activities
Capital expenditures		(25.1)	(25.8)	[2]
Acquisitions from Parent	[2]	481.6	210.6
Contributions to investment		(14)	0	[2]
Purchase price adjustment		0	0.4	[2]
Return of investment		32.6	10.5	[2]
April 2017 Divestiture	[2]	0	0.8
Net cash used in investing activities		(488.1)	(224.7)	[2]
Cash flows from financing activities
Net proceeds from equity offerings		973.3	2.9	[2]
Borrowings under credit facilities	[2]	1,220	580
Repayments of credit facilities		(972.9)	0	[2]
Contributions from general partner		20	0.1	[2]
Proceeds from April 2017 Divestiture		0	20.2	[2]
Capital distributions to general partner	[2]	(738.4)	(419.4)
Distributions to noncontrolling interests		(6.6)	(11.7)	[2]
Distributions to unitholders and general partner		(188.8)	(122.2)	[2]
Net distributions to Parent		0	(43.2)	[2]
Other contributions from Parent		5.9	12.4	[2]
Credit facility issuance costs		0	(0.7)	[2]
Other		(0.4)	(0.3)	[2]
Net cash provided by financing activities		312.1	18.1	[2]
Net increase in cash and cash equivalents		37.2	13.5	[2]
Cash and cash equivalents at beginning of the period		137.7	122.1	[2]
Cash and cash equivalents at end of the period		174.9	135.6	[2]
Non-cash investing and financing transactions
Distribution of working capital to Parent		0	(2.8)	[2]
Change in accrued capital expenditures		0.5	1.8	[2]
Other non-cash contributions from Parent		$ 1.9	$ 1.1	[2]
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.
[2]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

UNAUDITED CONDENSED CONSOLIDAT6

UNAUDITED CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (DEFICIT) - 6 months ended Jun. 30, 2018 - USD ($) $ in Millions	Total	Noncontrolling Interests	Common Unitholders	Common UnitholdersShell Pipeline Company L P	General PartnerShell Pipeline Company L P
Beginning balance at Dec. 31, 2017	$ (565.9)	$ 23.3	$ 2,773.5	$ (507.2)	$ (2,855.5)
Impact of change in accounting policy (Note 2) at Dec. 31, 2017	(2.3)	0.3	(1.4)	1	(2.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	180.2	5.5	64.5	51.6	58.6
Net proceeds from equity offerings	973.3		673.3	300
Contributions from general partner	20				20
Other contributions from Parent	7.7				7.7
Distributions to unitholders and general partner	(188.8)		(76)	(64.4)	(48.4)
Distributions to noncontrolling interests	(6.6)	(6.6)
May 2018 Acquisition	(738.4)				(738.4)
Ending balance at Jun. 30, 2018	$ (320.8)	$ 22.5	$ 3,433.9	$ (219)	$ (3,558.2)

Description of Business and Bas

Description of Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Except as noted within the context of each note disclosure, the dollar amounts presented in the tabular data within these note disclosures are stated in millions of dollars. The financial information for the three and six months ended June 30, 2017 has been retrospectively adjusted for the acquisition of businesses under common control (see Note 3 - Acquisitions and Divestiture). 1. Description of Business and Basis of Presentation Shell Midstream Partners, L.P. (“we,” “us,” “our” or “the Partnership”) is a Delaware limited partnership formed by Shell on March 19, 2014 to own and operate pipeline and other midstream assets, including certain assets acquired from Shell Pipeline Company LP (“SPLC”) and its affiliates. We conduct our operations either through our wholly owned subsidiary Shell Midstream Operating LLC (“Operating Company”) or through direct ownership by the Partnership. Our general partner is Shell Midstream Partners GP LLC (“general partner”). References to “RDS”, “Shell” or “Parent” refer collectively to Royal Dutch Shell plc and its controlled affiliates, other than us, our subsidiaries and our general partner. Our common units trade on the New York Stock Exchange under the symbol “SHLX”. Description of Business We are a fee-based, growth-oriented master limited partnership that owns, operates, develops and acquires pipelines and other midstream assets. As of June 30, 2018 , our assets include interests in entities that own crude oil and refined products pipelines and terminals that serve as key infrastructure to (i) transport onshore and offshore crude oil production to Gulf Coast and Midwest refining markets and (ii) deliver refined products from those markets to major demand centers. Our assets also include interests in entities that own natural gas and refinery gas pipelines that transport offshore natural gas to market hubs and deliver refinery gas from refineries and plants to chemical sites along the Gulf Coast. The following table reflects our ownership, and Shell’s retained ownership as of June 30, 2018 : SHLX Ownership Shell’s Retained Ownership Pecten Midstream LLC (“Pecten”) 100.0 % — % Sand Dollar Pipeline LLC (“Sand Dollar”) 100.0 % — % Triton West LLC (“Triton”) 100.0 % — % Zydeco Pipeline Company LLC (“Zydeco”) 92.5 % 7.5 % Amberjack Pipeline Company LLC (“Amberjack”) – Series A/Series B 75.0% / 50.0% — % Mars Oil Pipeline Company LLC (“Mars”) 71.5 % — % Odyssey Pipeline L.L.C. (“Odyssey”) 71.0 % — % Bengal Pipeline Company LLC (“Bengal”) 50.0 % — % Crestwood Permian Basin LLC (“Permian Basin”) 50.0 % — % LOCAP LLC (“LOCAP”) 41.48 % — % Poseidon Oil Pipeline Company LLC (“Poseidon”) 36.0 % — % Explorer Pipeline Company (“Explorer”) 12.62 % 25.97 % Proteus Oil Pipeline Company, LLC (“Proteus”) 10.0 % — % Endymion Oil Pipeline Company, LLC (“Endymion”) 10.0 % — % Colonial Pipeline Company (“Colonial”) 6.0 % 10.12 % Cleopatra Gas Gathering Company, LLC (“Cleopatra”) 1.0 % — % We generate a substantial portion of our revenue under long-term agreements by charging fees for the transportation, terminaling and storage of crude oil and refined products through our pipelines and storage tanks, and generate income from our equity and cost method investments. Our operations consist of one reportable segment. Basis of Presentation Our unaudited condensed consolidated financial statements include all subsidiaries required to be consolidated under generally accepted accounting principles in the United States (“GAAP”). Our reporting currency is U.S. dollars, and all references to dollars are U.S. dollars. The accompanying unaudited condensed consolidated financial statements and related notes have been prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete annual financial statements. The year-end condensed consolidated balance sheet data was derived from audited financial statements. During interim periods, we follow the accounting policies disclosed in our Annual Report on Form 10-K for the year ended December 31, 2017 (our “2017 Annual Report”), filed with the United States Securities and Exchange Commission (“SEC”). The unaudited condensed consolidated financial statements for the three and six months ended June 30, 2018 and 2017 include all adjustments we believe are necessary for a fair statement of the results of operations for the interim periods presented. These adjustments are of a normal recurring nature unless otherwise disclosed. Operating results for the interim periods are not necessarily indicative of the results that may be expected for the full year. These unaudited condensed consolidated financial statements and other information included in this Quarterly Report on Form 10-Q should be read in conjunction with our audited consolidated financial statements and notes thereto included in our 2017 Annual Report. Our consolidated subsidiaries include Pecten, Sand Dollar, Triton, Zydeco, Odyssey and the Operating Company. Asset acquisitions of additional interests in previously consolidated subsidiaries and interests in cost and equity method investments are included in the financial statements prospectively from the effective date of each acquisition. In cases where these types of acquisitions are considered acquisitions of businesses under common control, the financial statements are retrospectively adjusted. As such, all financial results of interests acquired in the May 2017 Acquisition and the December 2017 Acquisition (as defined in Note 3—Acquisitions and Divestiture ) have been retrospectively adjusted. For additional common control interests acquired of cost and equity method investments previously owned, only the incremental ownership interest has been retrospectively adjusted. Our unaudited condensed consolidated financial statements were derived from the financial statements and accounting records of SPLC and Shell for the periods prior to acquisition. Specifically, such businesses are reflected for the following periods prior to the effective date of such acquisitions by us: • May 2017 Acquisition for periods prior to May 10, 2017; and • December 2017 Acquisition for periods prior to December 1, 2017, including the effect of fully consolidating Odyssey. Our unaudited condensed consolidated statements of income and cash flow for the periods ended June 30, 2017 consist of the combined results of the May 2017 Acquisition and the December 2017 Acquisition prior to the respective acquisition dates, and the consolidated activity of the Partnership. Our unaudited condensed consolidated statement of income excludes the results of these businesses from net income attributable to the Partnership for the periods indicated above by allocating these results to our Parent. See Note 3 - Acquisitions and Divestiture for definitions and additional information. Summary of Significant Accounting Policies The accounting policies are set forth in Note 2—Summary of Significant Accounting Policies in the Notes to Consolidated Financial Statements of our 2017 Annual Report. There have been no significant changes to these policies during the six months ended June 30, 2018 , other than those noted below. Recent Accounting Pronouncements Standards Adopted as of January 1, 2018 In May 2014, the FASB issued Accounting Standards Update (“ASU”) 2014-09 to Topic 606, Revenue from Contracts with Customers, which superseded nearly all revenue recognition guidance in Topic 605, Revenue Recognition, under GAAP. We adopted the new standard utilizing the modified retrospective transition approach, effective January 1, 2018, by recognizing the cumulative effect of initially applying the standard for periods prior to January 1, 2018 to the opening balance of equity (deficit). See Note 2—Revenue Recognition for additional information and disclosures required by the new standard. In January 2017, the FASB issued ASU 2017-01 to Topic 805, Business Combinations, to clarify the definition of a business and to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This update was effective for us as of January 1, 2018. There was no impact on our financial statements as a result of this adoption in relation to our acquisition during the second quarter. In August 2016, the FASB issued ASU 2016-15 to Topic 230, Statement of Cash Flows, making changes to the classification of certain cash receipts and cash payments in order to reduce diversity in presentation. The update addresses eight specific cash flow issues, of which only one is applicable to our financial statements. The applicable update relates to distributions received from equity method investees and prescribes two options for presenting these cash flows: cumulative earnings approach or nature of the distribution approach. We will continue to apply the cumulative earnings approach, where distributions received are considered either returns on investment and classified as operating cash flows or returns of investment and classified as investing cash flows. The adoption of this update on January 1, 2018 did not have a material impact on our financial statements. In January 2016, the FASB issued ASU 2016-01 to Topic 825, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities, requiring equity investments (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. Additionally, the update allows equity investments that do not have readily determinable fair values to be re-measured at fair value either upon the occurrence of an observable price change or upon identification of impairment, and requires additional disclosure around those investments. We have the following three equity investments which are accounted for under the cost method and which do not have readily determinable fair values: June 30, 2018 December 31, 2017 Ownership Amount Ownership Amount Colonial 6.0 % $ 11.4 6.0 % $ 11.4 Explorer 12.62 % 48.6 12.62 % 48.6 Cleopatra 1.0 % 2.1 1.0 % 2.1 $ 62.1 $ 62.1 As of the adoption of this update on January 1, 2018, and as of June 30, 2018, we did not identify the occurrence of an observable price change or an identification of impairment for these three equity investments. Therefore, the adoption of this update on January 1, 2018 did not have a material impact on our financial statements. Standards Not Yet Adopted In February 2016, the FASB issued ASU 2016-02 to Topic 842, Leases, which requires lessees to recognize right-of-use assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either a financing lease or operating lease with classification affecting the pattern of expense recognition in the condensed consolidated statements of income and presentation of cash flows in the condensed consolidated statements of cash flows. This update also requires improved disclosures to help users of financial statements better understand the amount, timing and uncertainty of cash flows arising from leases. For lessors, this update modifies the classification criteria and the accounting for sales-type and direct financing leases. This update is effective on a modified retrospective basis for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. We will adopt the new standard on January 1, 2019 and continue to assess its impact to our consolidated financial statements and related disclosures. Currently, we plan to elect the practical expedients upon transition that will retain the lease classification and initial direct costs for any leases that exist prior to adoption. We will not reassess whether any contracts entered into prior to adoption are leases. In January 2018, the FASB issued ASU 2018-01 to provide an optional transition practical expedient to not evaluate existing or expired land easements that were not previously accounted for as leases under existing guidance. We intend to elect this practical expedient. In July 2018, the FASB issued ASU 2018-11 which provides entities an optional transitional relief method that allows entities to not apply the new guidance in the comparative periods they present in their financial statements in the year of adoption. This update also provides an optional practical expedient for lessors to avoid separating lease and associated non-lease components within a contract if certain criteria are met. We are evaluating this most recent update and continue to evaluate all other available transition practical expedients offered in connection with the new standard. As part of our implementation efforts to date, we have substantially completed the identification and aggregation of our lease contract population. We are reviewing these to determine the transition approach and assess the impact to our condensed consolidated financial statements upon adoption. We are also developing and starting to implement any necessary changes to existing processes and controls.

Revenue Recognition

Revenue Recognition	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition Adoption of ASC Topic 606, “Revenue from Contracts with Customers” On January 1, 2018, we adopted Topic 606 and all related ASU’s to this Topic (collectively, “the new revenue standard”) by applying the modified retrospective method to all contracts that were not completed on January 1, 2018. Results for reporting periods beginning after January 1, 2018 are presented in accordance with the new revenue standard, while prior period amounts are not adjusted and continue to be reported in accordance with our historic accounting under previous GAAP. We recorded a non-cash cumulative effect transition adjustment to increase total opening equity (deficit) of $4.5 million , with the impact primarily due to the earlier recognition of revenue related to deficiency payments under minimum volume commitment contracts. Additionally, we recorded a non-cash cumulative effect transition adjustment related to our equity method investment for Mars which resulted in a total net decrease to total opening equity (deficit) of $2.3 million . See Note 5 - Equity Method Investments for additional information. Revenue Recognition The new revenue standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The new revenue standard requires entities to recognize revenue through the application of a five-step model, which includes: identification of the contract; identification of the performance obligations; determination of the transaction price; allocation of the transaction price to the performance obligations; and recognition of revenue as the entity satisfies the performance obligations. Our revenues are primarily generated from the transportation, terminaling and storage of crude oil, refinery gas and refined petroleum products through our pipelines, terminals and storage tanks. To identify the performance obligations, we considered all the products or services promised in the contracts with customers, whether explicitly stated or implied based on customary business practices. Revenue is recognized when each performance obligation is satisfied under the terms of the contract. Each barrel of product transported or day of services provided is considered a distinct service that represents a performance obligation that would be satisfied over time if it were accounted for separately. The services provided over the contract period are a series of distinct services that are substantially the same, have the same pattern of transfer to the customer, and therefore, qualify as a single performance obligation. Since the customer simultaneously receives and consumes the benefits of services, we recognize revenue over time based on a measure of progress of volumes transported for transportation services contracts or number of days elapsed for storage and terminaling services contracts. Product revenue related to allowance oil sales is recognized at the point in time when the control of the oil transfers to the customer. For all performance obligations, payment is typically due in full within 30 days of the invoice date. Disaggregation of Revenue The following table provides information about disaggregated revenue by service type and customer type: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Transportation services revenue – third parties $ 54.7 $ 87.0 Transportation services revenue – related parties (1) 42.2 72.8 Total transportation services revenue 96.9 159.8 Storage services revenue – third parties 2.3 4.6 Storage services revenue – related parties 1.5 2.8 Total storage services revenue 3.8 7.4 Terminaling services revenue – third parties — — Terminaling services revenue – related parties 11.4 22.8 Total terminaling services revenue (2) 11.4 22.8 Product revenue – third parties 1.4 1.4 Product revenue – related parties 1.7 9.6 Total product revenue (3) 3.1 11.0 Total Topic 606 revenue 115.2 201.0 Lease revenue 14.1 27.9 Total revenue $ 129.3 $ 228.9 (1) Transportation services revenue - related parties for the three and six months ended June 30, 2018 includes $1.2 million and $2.4 million , respectively, of the non-lease service component in our transportation services contracts. (2) Terminaling services revenue is entirely comprised of the non-lease service component in our terminaling services contracts. (3) Product revenue is comprised of allowance oil sales. Transportation services revenue We have both long-term transportation contracts and month-to-month contracts for spot shippers that make nominations on our pipelines. Some of the long-term contracts entitle the customer to a specified amount of guaranteed capacity on the pipeline. Transportation services are charged at a per barrel rate or other applicable unit of measure. We apply the allocation exception guidance for variable consideration related to market indexing for long-term transportation contracts because (a) the variable payment relates specifically to our efforts to transfer the distinct service and (b) we allocate the variable amount of consideration entirely to the distinct service which is consistent with the allocation objective. Except for guaranteed capacity payments as discussed below, transportation services are billed monthly as services are rendered. Deferred revenue Our transportation services agreements on Zydeco entitle the customer to a specified amount of guaranteed capacity on the pipeline. This capacity cannot be pro-rated even if the pipeline is oversubscribed. In exchange, the customer makes a specified monthly payment regardless of the volume transported. If the customer does not ship its full guaranteed volume in a given month, it makes the full monthly cash payment (i.e., deficiency payments) and it may ship the unused volume in a later month for no additional cash payment for up to 12 months, subject to availability on the pipeline. The cash payment received is recognized as deferred revenue, a contract liability under the new revenue standard. If there is insufficient capacity on the pipeline to allow the unused volume to be shipped, the customer forfeits its right to ship such unused volume. We do not refund any cash payments relating to unused volumes. Deferred revenue under these arrangements was previously recognized into revenue once all contingencies or potential performance obligations associated with the related volumes had been satisfied or expired. Under the new revenue standard, we are required to estimate the likelihood that unused volumes will be shipped or forfeited at each reporting period based on additional data that becomes available and only to the extent that it is probable that a significant reversal of any incremental revenue will not occur. In some cases, this estimate could result in the earlier recognition of revenue. Storage and terminaling services revenue Storage and terminaling services are provided under short-term and long-term contracts, with a fixed price per month for committed storage and terminaling capacity, or under a monthly spot-rate for uncommitted storage or terminaling. Storage and terminaling services are billed monthly as services are rendered. Reimbursements from customers Under certain transportation, terminaling and storage service contracts, we receive reimbursements from customers to recover costs of construction, maintenance or operating costs either under a tariff surcharge per volume shipped or under separate reimbursement payments. Because we consider these amounts as consideration from customers associated with ongoing services to be provided to customers, we defer these payments in deferred revenue and recognize amounts in revenue over the life of the associated revenue contract as performance obligations are satisfied under the contract. We consider these payments to be revenue because control of the long-lived assets does not transfer to our customer upon completion. Our financial statements were not materially impacted by adoption of the new revenue standard related to reimbursements from customers. Lease revenue Certain of our long-term transportation and terminaling services contracts are accounted for as operating leases under Topic 840. These agreements have both a lease component and an implied operation and maintenance service component. We allocate the arrangement consideration between the lease components that fall within the scope of Topic 840 and any non-lease service components within the scope of the new revenue standard based on the relative stand-alone selling price of each component. We estimate the stand-alone selling price of the lease and non-lease service components based on an analysis of service-related and lease-related costs for each contract, adjusted for a representative profit margin. The contracts have a minimum fixed monthly payment for both the lease and non-lease service components. We present the non-lease service components under the new revenue standard within Transportation, terminaling and storage services revenue in the unaudited condensed consolidated statement of income. Product revenue We generate revenue by selling accumulated allowance oil inventory to customers. Sale of allowance oil is recorded as revenue, with specific cost based on a weighted average price per barrel recorded as cost of product sold. Our contracts and tariffs contain terms for the customer to reimburse us for losses from evaporation or other loss in transit in the form of allowance oil. We obtain control of the excess oil not lost during transportation, if any. Prior to the adoption of the new revenue standard, allowance oil received was recorded as revenue on a gross basis with the resulting actual gain or loss recorded in operations and maintenance expense. The subsequent sale of allowance oil, net of the product cost, was recorded as operations and maintenance expenses. Under the new revenue standard, we include the excess oil retained during the period, if any, as non-cash consideration and include this amount in the transaction price. Joint tariff Under the joint tariff agreement between Zydeco and LOCAP, revenues were historically recorded on a net basis as an agent prior to the adoption of the new revenue standard. However, subsequent to the adoption of the new revenue standard, because we control the transportation service before it is transferred to the customer, we are the principal and, therefore, record revenues from these agreements on a gross basis. Impact of adoption In accordance with the new revenue standard, the following tables summarize the impact of adoption on our unaudited condensed consolidated financial statements as of and for the three and six months ended June 30, 2018 : Three Months Ended June 30, 2018 Unaudited Condensed Consolidated Statement of Income As Reported Under Topic 606 Amounts Without Adoption of Topic 606 Effect of Change Increase/(Decrease) Revenue Transportation, terminaling and storage services – third parties $ 57.0 $ 57.3 $ (0.3 ) Transportation, terminaling and storage services – related parties 55.1 43.7 11.4 Product revenue – third parties 1.4 — 1.4 Product revenue – related parties 1.7 — 1.7 Lease revenue – related parties 14.1 26.6 (12.5 ) Costs and expenses Cost of product sold – third parties 1.2 — 1.2 Cost of product sold – related parties 1.2 — 1.2 Operations and maintenance – third parties 24.9 25.7 (0.8 ) Operations and maintenance – related parties 13.3 11.6 1.7 Net income 115.4 116.7 (1.3 ) Six Months Ended June 30, 2018 Unaudited Condensed Consolidated Statement of Income As Reported Under Topic 606 Amounts Without Adoption of Topic 606 Effect of Change Increase/(Decrease) Revenue Transportation, terminaling and storage services – third parties $ 91.6 $ 90.9 $ 0.7 Transportation, terminaling and storage services – related parties 98.4 75.8 22.6 Product revenue – third parties 1.4 — 1.4 Product revenue – related parties 9.6 — 9.6 Lease revenue – related parties 27.9 53.0 (25.1 ) Costs and expenses Cost of product sold – third parties 1.2 — 1.2 Cost of product sold – related parties 7.7 — 7.7 Operations and maintenance – third parties 68.0 69.0 (1.0 ) Operations and maintenance – related parties 26.7 22.4 4.3 Net income 180.2 183.1 (2.9 ) June 30, 2018 Unaudited Condensed Consolidated Balance Sheet As Reported Under Topic 606 Amounts Without Adoption of Topic 606 Effect of Change Increase/(Decrease) Deferred revenue – related party $ 6.7 $ 8.3 $ (1.6 ) Contract Balances We perform our obligations under a contract with a customer by providing services in exchange for consideration from the customer. The timing of our performance may differ from the timing of the customer’s payment, which results in the recognition of a contract asset or a contract liability. Although we did not have any contract assets as of June 30, 2018, we recognize a contract asset when we transfer goods or services to a customer and contractually bill an amount which is less than the revenue allocated to the related performance obligation. We recognize deferred revenue (contract liability) when the customer’s payment of consideration precedes our performance. The following table provides information about receivables and contract liabilities from contracts with customers: January 1, 2018 June 30, 2018 Receivables from contracts with customers – third parties $ 17.2 $ 19.7 Receivables from contracts with customers – related parties 18.8 17.3 Deferred revenue – third parties 5.5 4.8 Deferred revenue – related party 9.4 6.7 Significant changes in the deferred revenue balances with customers during the period are as follows: December 31, 2017 Transition Adjustment Additions (1) Reductions (2) June 30, 2018 Deferred revenue – third parties $ 5.5 — 3.4 (4.1 ) $ 4.8 Deferred revenue – related party $ 13.9 (4.5 ) 1.5 (4.2 ) $ 6.7 (1) Contract liability additions resulted from deficiency payments from minimum volume commitment contracts. (2) Contract liability reductions resulted from revenue earned through the actual or estimated use and expiration of deficiency credits. We currently have no assets recognized from the costs to obtain or fulfill a contract as of June 30, 2018 . Remaining Performance Obligations As of June 30, 2018 , contracts with remaining performance obligations primarily include minimum volume commitment contracts, long-term storage contracts and the service component of transportation and terminaling services contracts accounted for as operating leases. The following table includes revenue expected to be recognized in the future related to performance obligations exceeding one year of their initial terms that are unsatisfied or partially unsatisfied as of June 30, 2018 : Total 2018 2019 2020 2021 2022 and beyond Revenue expected to be recognized on multi-year committed shipper transportation contracts in place as of June 30, 2018 (1) $ 642.0 $ 102.2 $ 64.3 $ 50.1 $ 49.8 $ 375.6 Revenue expected to be recognized on other multi-year transportation service contracts in place as of June 30, 2018 (2) 47.7 2.7 5.4 5.4 5.4 28.8 Revenue expected to be recognized on multi-year storage service contracts in place as of June 30, 2018 6.0 2.0 4.0 — — — Revenue expected to be recognized on multi-year terminaling service contracts in place as of June 30, 2018 (2) 430.0 22.8 45.7 45.7 45.7 270.1 $ 1,125.7 $ 129.7 $ 119.4 $ 101.2 $ 100.9 $ 674.5 (1) Excludes revenue deferred for deficiency payments. (2) Relates to the non-lease service components of certain of our long-term transportation and terminaling service contracts which are accounted for as operating leases. As an exemption, we do not disclose the amount of remaining performance obligations for contracts with an original expected duration of one year or less or for variable consideration that is allocated entirely to a wholly unsatisfied promise to transfer a distinct service that forms part of a single performance obligation.

Acquisitions and Divestiture

Acquisitions and Divestiture	6 Months Ended
	Jun. 30, 2018
Business Combinations [Abstract]
Acquisitions and Divestiture	Acquisitions and Divestiture May 2018 Acquisition On May 11, 2018, we acquired SPLC’s ownership interests in Amberjack Pipeline Company LLC, a Delaware limited liability company (“Amberjack”), which is comprised of 75% of the issued and outstanding Series A membership interests of Amberjack and 50% of the issued and outstanding Series B membership interests of Amberjack for $1,220.0 million (the “May 2018 Acquisition”). The May 2018 Acquisition closed pursuant to a Purchase and Sale Agreement dated May 9, 2018 (the “May 2018 Purchase and Sale Agreement”) between us and SPLC, and is accounted for as a transaction between entities under common control on a prospective basis as an asset acquisition. We acquired historical carrying value of net assets under common control of $481.6 million which is included in Equity method investments in our unaudited condensed consolidated balance sheet. We recognized $738.4 million of consideration in excess of the historical carrying value of net assets acquired as a capital distribution to our general partner in accordance with our policy for common control transactions. We funded the May 2018 Acquisition with $494.0 million in borrowings under our Five Year Revolver due October 2019 (as defined in Note 8—Related Party Debt ) and $726.0 million in borrowings under our Five Year Revolver due December 2022 (as defined in Note 8—Related Party Debt ) with Shell Treasury Center (West) Inc. (“STCW”). 2017 Acquisitions During 2017, we completed two acquisitions, as described below, that were considered transfers of businesses between entities under common control, and therefore the related acquired assets and liabilities were transferred at historical carrying value. Because these acquisitions were common control transactions in which we acquired businesses, our historical financial statements have been retrospectively adjusted as if we owned the acquired assets and liabilities for all periods presented. December 2017 Acquisition On December 1, 2017, we acquired a 100% interest in Triton, 41.48% of the issued and outstanding membership interest in LOCAP, an additional 22.9% interest in Mars, an additional 22.0% interest in Odyssey, and an additional 10.0% interest in Explorer from SPLC and Equilon Enterprises LLC d/b/a Shell Oil Products US (“SOPUS”) for $825.0 million (the “December 2017 Acquisition”). The December 2017 Acquisition closed pursuant to a Purchase and Sale Agreement (the “December 2017 Purchase and Sale Agreement”) among the Operating Company, us, SPLC and SOPUS. SPLC and SOPUS are each wholly owned subsidiaries of Shell. We funded the cash consideration for the December 2017 Acquisition from $825.0 million in borrowings under the Five Year Revolver due December 2022 (as defined in Note 8—Related Party Debt ) and the Five Year Fixed Facility (as defined in Note 8—Related Party Debt) . May 2017 Acquisition On May 10, 2017, we acquired a 100% interest in Delta, Na Kika and Refinery Gas Pipeline for $630.0 million (the “May 2017 Acquisition”). As part of the May 2017 Acquisition, SPLC and Shell GOM Pipeline Company LP (“Shell GOM”) contributed all but the working capital of Delta and Na Kika to Pecten, and Shell Chemical LP (“Shell Chemical”) contributed all but the working capital of Refinery Gas Pipeline to Sand Dollar. The May 2017 Acquisition closed pursuant to a Purchase and Sale Agreement dated May 4, 2017 (the “May 2017 Purchase and Sale Agreement”), among the Operating Company, us, Shell Chemical, Shell GOM and SPLC. Shell Chemical, Shell GOM and SPLC are each wholly owned subsidiaries of Shell. We funded the May 2017 Acquisition with $50.0 million of cash on hand, $73.1 million in borrowings under our Five Year Revolver due October 2019 (as defined in Note 8—Related Party Debt ) and $506.9 million in borrowings under our Five Year Fixed Facility (as defined in Note 8—Related Party Debt ). Retrospective adjusted information tables The following tables present our results of operations and of cash flows giving effect to the December 2017 Acquisition. This acquisition is accounted for as a transaction between entities under common control and was retrospectively adjusted for the period of our Parent’s ownership prior to the transaction. The historical financial statements already include the effect of retrospectively adjusting for the May 2017 Acquisition. The results of the December 2017 Acquisition prior to the closing date of the acquisition are included in the acquisition column and the consolidated results are included in “Consolidated Results” within the tables below: Three Months Ended June 30, 2017 Shell Midstream Partners, L.P. (1) December 2017 Acquisition (2) Consolidated Results Revenue Transportation, terminaling and storage services – third parties $ 55.3 $ 4.4 $ 59.7 Transportation, terminaling and storage services – related parties 23.7 15.8 39.5 Lease revenue – related parties 7.8 5.4 13.2 Total revenue 86.8 25.6 112.4 Costs and expenses Operations and maintenance – third parties 22.9 3.6 26.5 Operations and maintenance – related parties 7.1 2.9 10.0 General and administrative – third parties 2.8 0.9 3.7 General and administrative – related parties 8.2 3.4 11.6 Depreciation, amortization and accretion 9.6 1.7 11.3 Property and other taxes 3.4 0.8 4.2 Total costs and expenses 54.0 13.3 67.3 Operating income 32.8 12.3 45.1 Income from equity method investments 37.2 7.5 44.7 Dividend income from cost investments 6.2 3.2 9.4 Investment and dividend income 43.4 10.7 54.1 Interest expense, net 7.5 — 7.5 Income before income taxes 68.7 23.0 91.7 Income tax expense — — — Net income 68.7 23.0 91.7 Less: Net income attributable to Parent 1.0 20.5 21.5 Less: Net income attributable to noncontrolling interests 2.2 2.5 4.7 Net income attributable to the Partnership $ 65.5 $ — $ 65.5 (1) As previously reported in our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2017, including the effect of retrospectively adjusting for the May 2017 Acquisition. (2) Our Parents’ results of the December 2017 Acquisition for the three months ended June 30, 2017. Six Months Ended June 30, 2017 Shell Midstream Partners, L.P. (1) December 2017 Acquisition (2) Consolidated Results Revenue Transportation, terminaling and storage services – third parties $ 110.8 $ 8.1 $ 118.9 Transportation, terminaling and storage services – related parties 52.6 31.3 83.9 Lease revenue – related parties 7.8 10.9 18.7 Total revenue 171.2 50.3 221.5 Costs and expenses Operations and maintenance – third parties 38.5 7.0 45.5 Operations and maintenance – related parties 18.2 5.5 23.7 General and administrative – third parties 4.6 1.1 5.7 General and administrative – related parties 16.6 7.1 23.7 Depreciation, amortization and accretion 19.1 3.5 22.6 Property and other taxes 7.6 1.5 9.1 Total costs and expenses 104.6 25.7 130.3 Operating income 66.6 24.6 91.2 Income from equity method investments 75.9 15.5 91.4 Dividend income from cost investments 13.5 6.0 19.5 Investment and dividend income 89.4 21.5 110.9 Interest expense, net 12.3 — 12.3 Income before income taxes 143.7 46.1 189.8 Income tax expense — — — Net income 143.7 46.1 189.8 Less: Net income attributable to Parent 3.0 41.0 44.0 Less: Net income attributable to noncontrolling interests 4.4 5.1 9.5 Net income attributable to the Partnership $ 136.3 $ — $ 136.3 (1) As previously reported in our Quarterly Report on Form 10-Q for the six months ended June 30, 2017, including the effect of retrospectively adjusting for the May 2017 Acquisition. (2) Our Parents’ results of the December 2017 Acquisition for the six months ended June 30, 2017. Six months Ended June 30, 2017 Shell Midstream Partners, L.P. (1) December 2017 Acquisition (2) Consolidated Results Cash flows from operating activities Net income $ 143.7 $ 46.1 $ 189.8 Adjustments to reconcile net income to net cash provided by operating activities Depreciation, amortization and accretion 19.1 3.5 22.6 Non-cash interest expense 0.1 — 0.1 Allowance oil reduction to net realizable value 0.3 — 0.3 Undistributed equity earnings (1.5 ) (2.7 ) (4.2 ) Changes in operating assets and liabilities Accounts receivable (14.2 ) (0.3 ) (14.5 ) Allowance oil 0.7 — 0.7 Prepaid expenses and other assets 1.8 0.1 1.9 Accounts payable 5.2 (0.6 ) 4.6 Deferred revenue and other unearned income 10.4 — 10.4 Accrued liabilities 9.7 (1.3 ) 8.4 Net cash provided by operating activities 175.3 44.8 220.1 Cash flows from investing activities Capital expenditures (20.9 ) (4.9 ) (25.8 ) Acquisitions from Parent (210.6 ) — (210.6 ) Purchase price adjustment 0.4 — 0.4 Return of investment 8.4 2.1 10.5 April 2017 Divestiture 0.8 — 0.8 Net cash used in investing activities (221.9 ) (2.8 ) (224.7 ) Cash flows from financing activities Net proceeds from public offerings 2.9 — 2.9 Borrowings under credit facility 580.0 — 580.0 Contributions from general partner 0.1 — 0.1 Proceeds from April 2017 Divestiture 20.2 — 20.2 Capital distributions to general partner (419.4 ) — (419.4 ) Distributions to noncontrolling interests (6.6 ) (5.1 ) (11.7 ) Distributions to unitholders and general partner (122.2 ) — (122.2 ) Net distributions to Parent (6.3 ) (36.9 ) (43.2 ) Other contributions from Parent 12.4 — 12.4 Credit facility issuance costs (0.7 ) — (0.7 ) Other (0.3 ) — (0.3 ) Net cash provided by (used in) financing activities 60.1 (42.0 ) 18.1 Net increase in cash and cash equivalents 13.5 — 13.5 Cash and cash equivalents at beginning of the period 121.9 0.2 122.1 Cash and cash equivalents at end of the period $ 135.4 $ 0.2 $ 135.6 Supplemental Cash Flow Information Non-cash investing and financing transactions Distribution of working capital to Parent $ (2.8 ) $ — $ (2.8 ) Change in accrued capital expenditures 2.7 (0.9 ) 1.8 Other non-cash contributions from Parent 1.1 — 1.1 (1) As previously reported in our Quarterly Report on Form 10-Q for the six months ended June 30, 2017, including the effect of retrospectively adjusting for the May 2017 Acquisition. (2) Our Parents’ results of the December 2017 Acquisition for the six months ended June 30, 2017. Divestiture On April 28, 2017, Zydeco divested a small segment of its pipeline system (the “April 2017 Divestiture”) to SOPUS as part of the Motiva JV separation. The April 2017 Divestiture closed pursuant to a Pipeline Sale and Purchase Agreement (the “April 2017 Pipeline Sale and Purchase Agreement”) dated April 28, 2017 among Zydeco and SOPUS. We received $21.0 million in cash consideration for this sale, of which $19.4 million is attributable to the Partnership. The cash consideration represents $0.8 million for the book value of net assets divested and $20.2 million in excess proceeds received from our Parent. The April 2017 Pipeline Sale and Purchase Agreement contained customary representations and warranties and indemnification by SOPUS.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Related party transactions include transactions with SPLC and Shell, including those entities in which Shell has an ownership interest but does not have control. Acquisition Agreements Refer to Note 3—Acquisitions and Divestiture for a description of applicable agreements. For a discussion of all other related party acquisition agreements, see Note 4—Related Party Transactions in the Notes to Consolidated Financial Statements of our 2017 Annual Report. Omnibus Agreement On November 3, 2014, we entered into an Omnibus Agreement with SPLC and our general partner concerning our payment of an annual general and administrative services fee to SPLC as well as our reimbursement of certain costs incurred by SPLC on our behalf. This agreement addresses the following matters: • our payment of an annual general and administrative fee of $8.5 million for the provision of certain services by SPLC; • our obligation to reimburse SPLC for certain direct or allocated costs and expenses incurred by SPLC on our behalf; • our obligation to reimburse SPLC for all expenses incurred by SPLC as a result of us becoming and continuing as a publicly traded entity; we will reimburse our general partner for these expenses to the extent the fees relating to such services are not included in the general and administrative fee; and • the granting of a license from Shell to us with respect to using certain Shell trademarks and trade names. Under the Omnibus Agreement, SPLC indemnified us against certain enumerated risks. Of those two indemnity obligations, one expired in 2017 and one remains. Under the remaining indemnification, SPLC agreed to indemnify us against tax liabilities relating to our initial assets that are identified prior to the date that is 60 days after the expiration of the statute of limitations applicable to such liabilities. This obligation has no threshold or cap. We in turn agreed to indemnify SPLC against events and conditions associated with the ownership or operation of our initial assets (other than any liabilities against which SPLC is specifically required to indemnify us as described above). During the six months ended June 30, 2018 , neither we nor SPLC made any claims for indemnification under the Omnibus Agreement. Tax Sharing Agreement For a discussion of the Tax Sharing Agreement, see Note 4—Related Party Transactions—Tax Sharing Agreement in the Notes to Consolidated Financial Statements of our 2017 Annual Report. Partnership Agreement On February 26, 2018, Shell Midstream Partners GP LLC, the general partner of the Partnership, executed Amendment No. 1 to the Partnership’s Amended and Restated Agreement of Limited Partnership dated November 3, 2014 (the “Amendment”), in response to changes to the Internal Revenue Code enacted by the Bipartisan Budget Act of 2015 relating to partnership audit and adjustment procedures. The Amendment did not have a material effect on our unaudited condensed consolidated financial statements. Noncontrolling Interests For Zydeco, noncontrolling interest consists of SPLC’s 7.5% retained ownership interest as of both June 30, 2018 and December 31, 2017 . For Odyssey, noncontrolling interest consists of GEL Offshore Pipeline LLC’s (“GEL”) 29.0% retained ownership interest as of both June 30, 2018 and December 31, 2017 . Other Related Party Balances Other related party balances consist of the following: June 30, 2018 December 31, 2017 Accounts receivable $ 24.8 $ 23.8 Prepaid expenses 4.9 11.9 Other assets 2.6 1.7 Accounts payable (1) 12.6 11.6 Deferred revenue 6.7 13.9 Accrued liabilities (2) 11.5 7.2 Debt payable (3) 2,091.5 1,844.0 (1) Accounts payable reflects amounts owed to SPLC for reimbursement of third party expenses incurred by SPLC for our benefit. (2) As of June 30, 2018 , accrued liabilities reflects $ 11.0 million accrued interest and $ 0.5 million other accrued liabilities. As of December 31, 2017, accrued liabilities reflects $ 6.6 million accrued interest and $ 0.6 million other accrued liabilities. (3) Debt payable reflects borrowings outstanding after taking into account unamortized debt issuance costs of $2.5 million and $2.9 million as of June 30, 2018 and December 31, 2017 , respectively. Related Party Credit Facilities We have entered into three credit facilities with STCW: the Five Year Revolver due December 2022, the Five Year Revolver due October 2019 and the Five Year Fixed Facility. Zydeco has also entered into the Zydeco Revolver with STCW. For definitions and additional information regarding these credit facilities, see Note 8—Related Party Debt in the Notes to Consolidated Financial Statements of our 2017 Annual Report. Related Party Revenues and Expenses We provide crude oil transportation, terminaling and storage services to related parties, primarily under long-term contracts. We entered into these contracts in the normal course of our business. Related party revenues consist of the following: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Transportation and terminaling services revenue – related parties $ 53.6 $ 38.1 $ 95.6 $ 80.6 Product revenue – related parties 1.7 — 9.6 — Storage services revenue – related parties 1.5 1.4 2.8 3.3 Lease revenue – related parties 14.1 13.2 27.9 18.7 Total revenue – related parties $ 70.9 $ 52.7 $ 135.9 $ 102.6 We have certain transportation and terminaling services agreements with related parties that are considered operating leases under GAAP. Certain of these agreements were entered into for terms of ten years with the option to extend for two additional five year terms, and we have additional agreements with an initial term of ten years with the option to extend for up to ten additional one year terms. As of June 30, 2018 , future minimum payments to be received under the ten -year contract term of these operating leases, which includes both the lease and non-lease service components of these leases, are estimated to be: Total Less than 1 year Years 2 to 3 Years 4 to 5 More than 5 years Operating leases $ 974.8 $ 106.4 $ 212.8 $ 212.8 $ 442.8 Beginning July 1, 2014, Zydeco entered into the Management Agreement with SPLC under which SPLC provides general management and administrative services to us. We no longer receive allocated corporate expenses from SPLC or Shell under this agreement. We will continue to receive direct and allocated field and regional expenses, including payroll expenses not covered under the Management Agreement. In addition, beginning October 1, 2015, Pecten entered into an operating and management agreement under which we receive direct and allocated field and regional expenses from SPLC. Beginning May 10, 2017, Sand Dollar entered into an operating and management agreement under which we receive direct and allocated expenses from SPLC. On December 1, 2017, our general partner, SPLC and Triton entered into an operating and administrative management agreement pursuant to which we receive direct and allocated expenses from our general partner. On December 1, 2017, our general partner, SPLC and Odyssey entered into an operating and administrative management agreement pursuant to which we receive direct and allocated expenses from our general partner. The expenses under these agreements are primarily allocated to us on the basis of headcount, labor or other measure. These expense allocations have been determined on a basis that both SPLC and we consider to be a reasonable reflection of the utilization of services provided or the benefit received by us during the periods presented. For a discussion of these agreements, see Note 4—Related Party Transactions in the Notes to Consolidated Financial Statements of our 2017 Annual Report. The majority of our insurance coverage is provided by a wholly owned subsidiary of Shell with the remaining coverage provided by third-party insurers. The related party portion of insurance expense for the three and six months ended June 30, 2018 was $3.7 million and $7.3 million , respectively, and for the three and six months ended June 30, 2017 was $1.4 million and $3.4 million , respectively. The following table shows related party expenses, including personnel costs described above, incurred by Shell and SPLC on our behalf that are reflected in the accompanying unaudited condensed consolidated statements of income for the indicated periods: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Operations and maintenance – related parties $ 13.3 $ 10.0 $ 26.7 $ 23.7 General and administrative – related parties 13.9 11.6 26.8 23.7 For a discussion of services performed by Shell on our behalf, see Note 1 - Description of Business and Basis of Presentation - Basis of Presentation in the Notes to Consolidated Financial Statements of our 2017 Annual Report. Pursuant to various operating and administrative management agreements described above, we are allocated indirect operating and general corporate expenses from Shell. Our allocated share of operating expenses, which are included within operations and maintenance – related parties, for the three and six months ended June 30, 2018 were $3.0 million and $7.4 million , respectively, and for the three and six months ended June 30, 2017 were $3.4 million and $7.6 million , respectively. Additionally, our allocated share of general corporate expenses, which are included within general and administrative expenses – related parties, during the three and six months ended June 30, 2018 were $8.3 million and $15.9 million , respectively, and for the three and six months ended June 30, 2017 were $6.3 million and $13.5 million , respectively. Included in these general and administrative expenses for the three and six months ended June 30, 2018 are $2.2 million and $4.3 million , respectively, under the Management Agreement and $2.1 million and $4.2 million , respectively, under the Omnibus Agreement. Included in these general and administrative expenses for the three and six months ended June 30, 2017 are $2.0 million and $4.0 million , respectively, under the Management Agreement and $2.1 million and $4.2 million , respectively, under the Omnibus Agreement. Pension and Retirement Savings Plans Employees who directly or indirectly support our operations participate in the pension, postretirement health and life insurance, and defined contribution benefit plans sponsored by Shell, which include other Shell subsidiaries. Our share of pension and postretirement health and life insurance costs for the three and six months ended June 30, 2018 were $1.7 million and $3.3 million , respectively, and for the three and six months ended June 30, 2017 were $1.5 million and $3.1 million , respectively. Our share of defined contribution benefit plan costs for both the three and six months ended June 30, 2018 were $0.7 million and $1.3 million , respectively, and for the three and six months ended June 30, 2017 were $0.6 million and $1.2 million , respectively. Pension and defined contribution benefit plan expenses are included in either general and administrative expenses - related parties or operations and maintenance expenses - related parties in the accompanying unaudited condensed consolidated statements of income, depending on the nature of the employee’s role in our operations. Equity and Cost Method Investments We have equity and cost method investments in entities, including Colonial and Explorer, in which SPLC also owns interests. In some cases, we may be required to make capital contributions or other payments to these entities. See Note 5 – Equity Method Investments for additional details. Reimbursements The following table reflects reimbursements from our Parent for the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Cash received (1) $ 4.8 $ 6.8 $ 5.9 $ 9.4 Changes in receivable from Parent (2) (3.1 ) (2.7 ) 0.2 1.1 Total reimbursements (3) $ 1.7 $ 4.1 $ 6.1 $ 10.5 (1) These reimbursements are included in Other contributions from Parent in the accompanying consolidated statements of cash flows. (2) These reimbursements are included in Other non-cash contributions from Parent in the accompanying consolidated statements of cash flows. (3) These reimbursements are included in Other contributions from Parent in the accompanying consolidated statements of equity (deficit) and are exclusive of $1.6 million for the six months ended June 30, 2018 related to contributions from Parent. During the three and six months ended June 30, 2018 , we filed claims for reimbursement from our Parent of $1.7 million and $6.1 million . This reflects our proportionate share of the Zydeco directional drill project costs and expenses. During the three and six months ended June 30, 2017, we filed claims for reimbursement from our parent of $4.1 million and $10.5 million , respectively. This reflects our proportionate share of Zydeco directional drill project costs and expenses of $3.5 million and $9.9 million , respectively. Additionally, this includes reimbursement for the Refinery Gas Pipeline gas to butane service conversion project of $0.6 million for both the three and six months ended June 30, 2017.

Equity Method Investments

Equity Method Investments	6 Months Ended
	Jun. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Equity Method Investments For each of the following investments, we have the ability to exercise significant influence over these investments based on certain governance provisions and our participation in the significant activities and decisions that impact the management and economic performance of the investments. Equity method investments comprise the following as of the dates indicated: June 30, 2018 December 31, 2017 Ownership Investment Amount Ownership Investment Amount Amberjack – Series A / Series B 75.0% / 50.0% $ 465.7 —% $ — Mars 71.5% 168.9 71.5% 187.4 Bengal 50.0% 80.6 50.0% 79.7 Permian Basin 50.0% 61.5 50.0% 49.4 LOCAP 41.48% 8.4 41.48% 6.9 Poseidon 36.0% — 36.0% 2.3 Proteus 10.0% 16.8 10.0% 17.4 Endymion 10.0% 19.0 10.0% 19.5 $ 820.9 $ 362.6 Unamortized differences in the basis of the initial investments and our interest in the separate net assets within the financial statements of the investees are amortized into net income over the remaining useful lives of the underlying assets. As of June 30, 2018 and December 31, 2017 , the unamortized basis differences included in our equity investments are $42.2 million and $41.4 million , respectively. For the three and six months ended June 30, 2018 , the net amortization expense was $0.9 million and $1.9 million , respectively, and for the three and six months ended June 30, 2017 , the net amortization expense was $0.9 million and $1.9 million , respectively. During the first quarter of 2018, the investment amount for Poseidon was reduced to zero due to distributions received that were in excess of our investment balance and we, therefore, suspended the equity method of accounting. As we have no commitments to provide further financial support to Poseidon, we have recorded excess distributions of $8.9 million and $9.6 million , respectively, in Other income in our unaudited condensed consolidated statement of income for the three and six months ended June 30, 2018. Once our cumulative share of equity earnings becomes greater than the amount of distributions received, we will resume the equity method of accounting as long as the equity method investment balance remains greater than zero. Our equity method investments balance was affected by the following during the periods indicated: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Distributions Received Income from Equity Investments Distributions Received Income from Equity Investments Impact of Change in Accounting Policy Amberjack (1) $ 31.9 $ 16.0 $ 31.9 $ 16.0 $ — Mars 25.4 21.2 57.6 46.0 (6.9 ) Bengal 4.9 5.4 8.9 9.8 — Poseidon (2) 8.9 — 18.3 6.4 — Other (3) 6.3 5.8 11.8 10.4 — $ 77.4 $ 48.4 $ 128.5 $ 88.6 $ (6.9 ) (1) We acquired an interest in Amberjack in the May 2018 Acquisition. The acquisition of this interest has been accounted for prospectively. (2) As stated above, the equity method of accounting has been suspended for Poseidon and excess distributions are recorded as Other Income. (3) Included in Other is the activity associated with our investments in Permian Basin, LOCAP, Proteus and Endymion. We acquired a 50.0% interest in Permian Basin in October 2017 from a third party. The acquisition of this interest has been accounted for prospectively. Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 Distributions Received Income from Equity Investments Distributions Received Income from Equity Investments Purchase Price Adjustment Mars (1) $ 27.9 $ 29.7 $ 62.2 $ 61.3 $ — Bengal 4.6 5.4 9.3 10.7 — Poseidon 9.3 6.4 19.3 13.2 — Other (2) 5.3 3.2 6.9 6.2 (0.4 ) $ 47.1 $ 44.7 $ 97.7 $ 91.4 $ (0.4 ) (1) We acquired an additional 22.9% interest in Mars in the December 2017 Acquisition. The financial information presented for the three and six months ended June 30, 2017 has been retrospectively adjusted for the incremental ownership acquired. (2) Included in Other is the activity associated with our investments in LOCAP, Proteus and Endymion. We acquired a 41.48% interest in LOCAP in the December 2017 Acquisition. The financial information presented for the three and six months ended June 30, 2017 has been retrospectively adjusted for the ownership acquired. See Note 3 - Acquisitions and Divestiture for additional information regarding the acquisitions of our equity investments. We acquired an additional 22.0% interest in Odyssey on December 1, 2017, which is now being consolidated for all periods presented in these financial statements. The adoption date of the new revenue standard for the majority of our equity method investments will follow the non-public business entity adoption date of January 1, 2019 for their stand-alone financial statements, with the exception of Mars and Permian Basin. As a result of adoption of the new revenue standard on January 1, 2018, we recognized our proportionate share of cumulative effect transition adjustments as a decrease to equity (deficit) in the amount of $6.9 million under the modified retrospective transition method, which was due to the Mars transition adjustment on its transportation and dedication agreements which resulted in a deferral of revenue. Summarized Financial Information The following tables present aggregated selected unaudited income statement data for our equity method investments (on a 100% basis): Three Months Ended June 30, 2018 Total revenues Total operating expenses Operating income Net income Statements of Income Amberjack (1) $ 69.9 $ 17.5 $ 52.4 $ 52.5 Mars 51.8 21.3 30.5 30.5 Bengal 18.1 7.4 10.7 10.7 Poseidon 27.3 7.9 19.4 17.4 Other (2) 38.8 14.7 24.1 21.4 (1) Although our interest in Amberjack was acquired on May 11, 2018, the financial results for the full three months ended June 30, 2018 is presented for comparability. (2) Included in Other is the activity associated with our investments in Permian Basin, LOCAP, Proteus and Endymion. Six Months Ended June 30, 2018 Total revenues Total operating expenses Operating income Net income Statements of Income Amberjack (1) $ 132.0 $ 36.2 $ 95.8 $ 95.9 Mars 109.0 43.0 66.0 66.0 Bengal 33.5 14.2 19.3 19.3 Poseidon 56.2 16.5 39.7 36.0 Other (2) 75.4 30.2 45.2 40.2 (1) Although our interest in Amberjack was acquired on May 11, 2018, the financial results for the full six months ended June 30, 2018 is presented for comparability. (2) Included in Other is the activity associated with our investments in Permian Basin, LOCAP, Proteus and Endymion. Three Months Ended June 30, 2017 Total revenues Total operating expenses Operating income Net income Statements of Income Mars $ 66.4 $ 24.3 $ 42.1 $ 42.1 Bengal 18.1 7.1 11.0 10.9 Poseidon 28.5 8.5 20.0 18.6 Other (1) 29.8 10.2 19.6 14.7 (1) Included in Other is the activity associated with our investments in LOCAP, Proteus and Endymion. Six Months Ended June 30, 2017 Total revenues Total operating expenses Operating income Net income Statements of Income Mars $ 131.3 $ 44.2 $ 87.1 $ 87.1 Bengal 35.9 14.3 21.6 21.5 Poseidon 57.4 16.6 40.8 38.0 Other (1) 58.8 20.0 38.8 29.8 (1) Included in Other is the activity associated with our investments in LOCAP, Proteus and Endymion. Capital Contributions In accordance with the Member Interest Purchase Agreement entered into in conjunction with the acquisition of Permian Basin in October 2017, we will make capital contributions for our pro rata interest in Permian Basin to fund capital and other expenditures, as approved by supermajority ( 75% ) vote of the members. We made capital contributions of $14.0 million in the second quarter of 2018.

Property, Plant and Equipment

Property, Plant and Equipment	6 Months Ended
	Jun. 30, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment consist of the following as of the dates indicated: Depreciable Life June 30, 2018 December 31, 2017 Land — $ 8.2 $ 8.2 Building and improvements 10 - 40 years 38.9 38.9 Pipeline and equipment (1) 10 - 30 years 1,155.8 1,153.6 Other 5 - 25 years 17.8 17.8 1,220.7 1,218.5 Accumulated depreciation and amortization (2) (548.5 ) (526.1 ) 672.2 692.4 Construction in progress 69.0 44.1 Property, plant and equipment, net $ 741.2 $ 736.5 (1) As of June 30, 2018 and December 31, 2017, includes cost of $357.9 million and $353.7 million , respectively, related to assets under operating lease (as lessor), which commenced in May 2017 and December 2017. As of both June 30, 2018 and December 31, 2017, includes cost of $22.8 million related to assets under capital lease (as lessee). (2) As of June 30, 2018 and December 31, 2017, includes accumulated depreciation of $111.2 million and $104.7 million , respectively, related to assets under operating lease (as lessor), which commenced in May 2017 and December 2017. As of June 30, 2018 and December 31, 2017, includes accumulated depreciation of $3.7 million and $3.0 million , respectively, related to assets under capital lease (as lessee). Depreciation and amortization expense on property, plant and equipment for the three and six months ended June 30, 2018 was $11.4 million and $22.8 million , respectively, and for the three and six months ended June 30, 2017 was $11.3 million and $22.6 million , respectively. Depreciation and amortization expense is included in cost and expenses in the accompanying condensed consolidated statements of income. Depreciation and amortization expense on property, plant and equipment includes amounts pertaining to assets under operating (as lessor) and capital leases (as lessee).

Accrued Liabilities - Third Par

Accrued Liabilities - Third Parties	6 Months Ended
	Jun. 30, 2018
Payables and Accruals [Abstract]
Accrued Liabilities - Third Parties	Accrued Liabilities – Third Parties Accrued liabilities – third parties consist of the following as of the dates indicated: June 30, 2018 December 31, 2017 Transportation, project engineering $ 15.1 $ 6.0 Property taxes 9.2 4.2 Other accrued liabilities 2.2 2.5 Total accrued liabilities – third parties $ 26.5 $ 12.7 See Note 4—Related Party Transactions for a discussion of accrued liabilities – related parties.

Related Party Debt

Related Party Debt	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Related Party Debt	Related Party Debt Consolidated related party debt obligations comprise the following as of the dates indicated: June 30, 2018 December 31, 2017 Outstanding Balance Total Capacity Available Capacity Outstanding Balance Total Capacity Available Capacity Five Year Revolver due December 2022 $ 1,000.0 $ 1,000.0 $ — $ 1,000.0 $ 1,000.0 $ — Five Year Fixed Facility 600.0 600.0 — 600.0 600.0 — Five Year Revolver due October 2019 (1) 494.0 760.0 266.0 246.9 760.0 513.1 Zydeco Revolver — 30.0 30.0 — 30.0 30.0 Unamortized debt issuance costs (2.5 ) n/a n/a (2.9 ) n/a n/a Debt payable – related party $ 2,091.5 $ 2,390.0 $ 296.0 $ 1,844.0 $ 2,390.0 $ 543.1 (1) On August 1, 2018, the Partnership extended the maturity date. See Note 13 – Subsequent Events for additional information. For the three and six months ended June 30, 2018 , interest and fee expenses associated with our borrowings were $12.9 million and $22.9 million , respectively, of which we paid $7.4 million and $18.5 million , respectively. For the three and six months ended June 30, 2017 , interest and fee expenses associated with our borrowings were $6.7 million and $10.7 million , respectively, of which we paid $4.0 million and $7.7 million , respectively. Borrowings under our revolving credit facilities approximate fair value as the interest rates are variable and reflective of market rates, which results in a Level 2 instrument. The fair value of our Loan Facility Agreement with STCW with a borrowing capacity of $600.0 million (the “ Five Year Fixed Facility”) is estimated based on the published market prices for issuances of similar risk and tenor and is categorized as a Level 2 instrument. As of June 30, 2018 , the carrying amount and estimated fair value of total debt (before amortization of issuance costs) was $2,094.0 million and $2,088.5 million , respectively. As of December 31, 2017 , the carrying amount and estimated fair value of total debt (before amortization of issuance costs) was $1,846.9 million and $1,858.4 million , respectively. On May 11, 2018, we funded the May 2018 Acquisition with $494.0 million in borrowings under our five year revolving credit facility with STCW due October 2019 (the “ Five Year Revolver due October 2019”) and $726.0 million in borrowings under our five year credit facility due December 2022 (the “ Five Year Revolver due December 2022”). On February 6, 2018, we used net proceeds from sales of common units and from our general partner’s proportionate capital contribution to repay $246.9 million of borrowings outstanding under our Five Year Revolver due October 2019 and $726.0 million of borrowings outstanding under our Five Year Revolver due December 2022. For additional information on our credit facilities, refer to Note 8 – Related Party Debt in the Notes to Consolidated Financial Statements in our 2017 Annual Report. Borrowings and repayments under our credit facilities for the six months ended June 30, 2018 and 2017 are disclosed in our unaudited condensed consolidated statements of cash flows. See Note 3 – Acquisitions and Divestiture for additional information regarding our use of borrowings. See Note 9 – Equity (Deficit) for additional information regarding the source of our repayments.

Equity (Deficit)

Equity (Deficit)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Equity (Deficit)	Equity (Deficit) Our capital accounts are comprised of 2% general partner interests and 98% limited partner interests. The common units represent limited partner interests in us. The holders of common units, both public and SPLC, are entitled to participate in partnership distributions and have limited rights of ownership as provided for under our partnership agreement. Our general partner participates in our distributions and also currently holds incentive distribution rights (“IDR’s”) that entitle it to receive increasing percentages of the cash we distribute from operating surplus. At-the-Market Program On March 2, 2016, we commenced an “at-the-market” equity distribution program pursuant to which we may issue and sell common units for up to $300.0 million in gross proceeds. During the six months ended June 30, 2018 , we did not have any sales under this program. During the quarter ended June 30, 2017, we completed the sale of 94,925 common units under this program for $2.9 million net proceeds ( $3.0 million gross proceeds, or an average price of $31.51 per common unit, less $0.1 million of transaction fees). In connection with the issuance of the common units, we issued 1,938 general partner units to our general partner for $0.1 million in order to maintain its 2% general partner interest in us. We used proceeds from these sales of common units and from our general partner's proportionate capital contribution for general partnership purposes. Public Offering and Private Placement On February 6, 2018, we completed the sale of 25,000,000 common units in a registered public offering for $673.3 million net proceeds ( $680.0 million gross proceeds, or $27.20 per common unit, less $6.0 million of underwriter’s fees and $0.7 million of transaction fees). In connection with the issuance of common units, we issued 510,204 general partner units to our general partner for $13.9 million in order to maintain its 2% general partner interest in us. On February 6, 2018, we also completed the sale of 11,029,412 common units in a private placement with Shell Midstream LP Holdings LLC, an indirect subsidiary of Shell, for an aggregate purchase price of $300.0 million , or $27.20 per common unit. In connection with the issuance of the common units, we issued 225,091 general partner units to the general partner for $6.1 million in order to maintain its 2% general partner interest in us. We used net proceeds from sales of common units and from our general partner’s proportionate capital contribution to repay $246.9 million of borrowings outstanding under the Five Year Revolver due October 2019 and $726.0 million of borrowings outstanding under the Five Year Revolver due December 2022, as well as for general partnership purposes. Units Outstanding As of June 30, 2018 , we had 223,811,781 common units outstanding, of which 123,832,233 were publicly owned. SPLC owned 99,979,548 common units, representing an aggregate 43.8% limited partner interest in us, all of the incentive distribution rights, and 4,567,588 general partner units, representing a 2.0% general partner interest in us. The changes in the number of units outstanding from December 31, 2017 through June 30, 2018 are as follows: Public SPLC General (in units) Common Common Partner Total Balance as of December 31, 2017 98,832,233 88,950,136 3,832,293 191,614,662 Units issued in connection with equity offerings 25,000,000 11,029,412 735,295 36,764,707 Balance as of June 30, 2018 123,832,233 99,979,548 4,567,588 228,379,369 Expiration of Subordination Period On February 15, 2017, all of the subordinated units converted into common units following the payment of the cash distribution for the fourth quarter of 2016. Each of our 67,475,068 outstanding subordinated units converted into one common unit. The converted units participated pro rata with the other common units in distributions of available cash. The conversion of the subordinated units did not impact the amount of cash distributions paid by us or the total number of outstanding units. Distributions to our Unitholders The following table details the distributions declared and/or paid for the periods presented: Date Paid or Public SPLC SPLC General Partner Distributions to be Paid Three Months Ended Common Common Subordinated IDR's 2% Total (in millions, except per unit amounts) February 14, 2017 December 31, 2016 $ 24.5 $ 5.9 $ 18.7 $ 8.3 $ 1.2 $ 58.6 $ 0.27700 May 12, 2017 March 31, 2017 25.7 25.9 — 10.7 1.3 63.6 0.29100 August 14, 2017 June 30, 2017 26.9 27.0 — 12.9 1.4 68.2 0.30410 November 14, 2017 September 30, 2017 31.4 28.3 — 16.2 1.5 77.4 0.31800 February 14, 2018 December 31, 2017 32.9 29.6 — 18.9 1.7 83.1 0.33300 May 15, 2018 March 31, 2018 43.1 34.8 — 25.7 2.1 105.7 0.34800 August 14, 2018 June 30, 2018 (1) 45.2 36.5 — 29.4 2.3 113.4 0.36500 (1) For more information see Note 13 — Subsequent Events . Distributions to Noncontrolling Interests Distributions to SPLC for its noncontrolling interest in Zydeco for both the three and six months ended June 30, 2018 were $2.9 million , and for the three and six months ended June 30, 2017 were $3.4 million and $6.6 million , respectively. Distributions to GEL for its noncontrolling interest in Odyssey for the three and six months ended June 30, 2018 were $1.8 million and $3.7 million , respectively, and for the three and six months ended June 30, 2017 were $2.6 million and $5.1 million , respectively. See Note 4—Related Party Transactions for additional details.

Net Income Per Limited Partner

Net Income Per Limited Partner Unit	6 Months Ended
	Jun. 30, 2018
Partners' Capital Notes [Abstract]
Net Income Per Limited Partner Unit	Net Income Per Limited Partner Unit Net income per unit applicable to common limited partner units, and to subordinated limited partner units in periods prior to the expiration of the subordination period, is computed by dividing the respective limited partners’ interest in net income attributable to the Partnership for the period by the weighted average number of common units and subordinated units, respectively, outstanding for the period. Because we have more than one class of participating securities, we use the two-class method when calculating the net income per unit applicable to limited partners. The classes of participating securities include common units, subordinated units, general partner units and IDR’s. Basic and diluted net income per unit are the same because we do not have any potentially dilutive units outstanding for the period presented. Our net income includes earnings related to businesses acquired through transactions between entities under common control for periods prior to their acquisition by us. We have allocated these pre-acquisition earnings to our general partner. The following tables show the allocation of net income attributable to the Partnership to arrive at net income per limited partner unit: Three Months Ended Six Months Ended 2018 2017 2018 2017 Net income $ 115.4 $ 91.7 $ 180.2 $ 189.8 Less: Net income attributable to Parent — 21.5 — 44.0 Net income attributable to noncontrolling interests 4.7 4.7 5.5 9.5 Net income attributable to the Partnership 110.7 65.5 174.7 136.3 Less: General Partner’s distribution declared 31.7 14.3 59.5 26.3 Limited Partners’ distribution declared on common units 81.7 53.9 159.6 105.5 Income (less than) / in excess of distributions $ (2.7 ) $ (2.7 ) $ (44.4 ) $ 4.5 Three Months Ended June 30, 2018 General Partner Limited Partners ’ Common Units Total (in millions of dollars, except per unit data) Distributions declared $ 31.7 $ 81.7 $ 113.4 Distributions in excess of income (0.1 ) (2.6 ) (2.7 ) Net income attributable to the Partnership $ 31.6 $ 79.1 $ 110.7 Weighted average units outstanding (in millions): Basic and diluted 223.8 Net income per Limited Partner Unit (in dollars): Basic and diluted $ 0.35 Six Months Ended June 30, 2018 General Partner Limited Partners ’ Common Units Total (in millions of dollars, except per unit data) Distributions declared $ 59.5 $ 159.6 $ 219.1 Distributions in excess of income (0.9 ) (43.5 ) (44.4 ) Net income attributable to the Partnership $ 58.6 $ 116.1 $ 174.7 Weighted average units outstanding (in millions): Basic and diluted 216.7 Net income per Limited Partner Unit (in dollars): Basic and diluted $ 0.54 Three Months Ended June 30, 2017 General Partner Limited Partners ’ Common Units Total (in millions of dollars, except per unit data) Distributions declared $ 14.3 $ 53.9 $ 68.2 Income in excess of distributions — (2.7 ) (2.7 ) Net income attributable to the Partnership $ 14.3 $ 51.2 $ 65.5 Weighted average units outstanding (in millions) (1) : Basic and diluted 177.4 Net income per Limited Partner Unit (in dollars): Basic and diluted $ 0.29 Six Months Ended June 30, 2017 General Partner Limited Partners ’ Common Units Total (in millions of dollars, except per unit data) Distributions declared $ 26.3 $ 105.5 $ 131.8 Income in excess of distributions 0.1 4.4 4.5 Net income attributable to the Partnership $ 26.4 $ 109.9 $ 136.3 Weighted average units outstanding (in millions) (1) : Basic and diluted 177.3 Net income per Limited Partner Unit (in dollars): Basic and diluted $ 0.62 (1) The subordinated units converted into common units on February 15, 2017 and were considered outstanding common units for the entire period with respect to the weighted average number of units outstanding.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We are not a taxable entity for U.S. federal income tax purposes or for the majority of states that impose an income tax. Taxes on our net income are generally borne by our partners through the allocation of taxable income. Our income tax expense results from partnership activity in the state of Texas, as conducted by Zydeco, Sand Dollar and Triton. Income tax expense for both the three and six months ended June 30, 2018 and 2017 was immaterial. On December 22, 2017, the Tax Cuts and Jobs Act (the “TCJA”) was signed into law by President Trump. The TCJA makes broad and complex changes to the Internal Revenue Code of 1986, including, but not limited to, (1) creating a new deduction on certain pass-through income to individual partners; (2) repealing the partnership technical termination rule; (3) creating new limitations on certain deductions and credits, including interest expense deductions; and (4) reducing the highest marginal U.S. federal corporate income tax rate from 35% to 21% for tax years beginning after December 31, 2017. With the exception of the operations of Colonial, Explorer and LOCAP, which are treated as corporations for federal income tax purposes, the operations of the Partnership are not subject to federal income tax, and therefore, we believe the TCJA will not have a material impact to the Partnership for 2018.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Environmental Matters We are subject to federal, state, and local environmental laws and regulations. We routinely conduct reviews of potential environmental issues and claims that could impact our assets or operations. These reviews assist us in identifying environmental issues and estimating the costs and timing of remediation efforts. In making environmental liability estimations, we consider the material effect of environmental compliance, pending legal actions against us and potential third-party liability claims. Often, as the remediation evaluation and effort progresses, additional information is obtained, requiring revisions to estimated costs. These revisions are reflected in our income in the period in which they are probable and reasonably estimable. As of both June 30, 2018 and December 31, 2017 , we had $0.3 million of accrued liabilities associated with environmental clean-up costs. This accrued liability relates to a Consent Decree issued in 1998 by the State of Washington Department of Ecology with respect to our products terminal located in Seattle, Washington. The costs relate to ongoing groundwater compliance monitoring and other remedial activities. Legal Proceedings We are named defendants in lawsuits and governmental proceedings that arise in the ordinary course of business. For each of our outstanding legal matters, we evaluate the merits of the case, our exposure to the matter, possible legal or settlement strategies and the likelihood of an unfavorable outcome. While there are still uncertainties related to the ultimate costs we may incur, based upon our evaluation and experience to date, we do not expect that the ultimate resolution of these matters will have a material adverse effect on our financial position, operating results, or cash flows. Indemnification Under our Omnibus Agreement, certain environmental liabilities, tax liabilities, litigation and other matters attributable to the ownership or operation of our assets prior to the IPO are indemnified by SPLC. Other than tax liabilities for which the statute of limitations has not expired, the obligations of SPLC under the Omnibus Agreement expired prior to 2018. See Note 4 - Related Party Transactions for additional information. Minimum Throughput On September 1, 2016, the in-service date of the capital lease for the Port Neches storage tanks, a joint tariff agreement with a third party became effective and requires monthly payments of approximately $0.4 million . The tariff will be reviewed annually and the rate updated based on the Federal Energy Regulatory Commission (“FERC”) indexing adjustment effective July 1 of each year. Effective July 1, 2018, there was an approximately 4.4% increase to this rate based on FERC indexing adjustment. The initial term of the agreement is ten years with automatic one year renewal terms with the option to cancel prior to each renewal period. Other Commitments We hold cancelable easements or rights-of-way arrangements from landowners permitting the use of land for the construction and operation of our pipeline systems. Obligations under these easements are not material to the results of our operations. Leases We have an operating lease for land, lease of platform space, tie-in agreement and a capital lease for storage tanks. See Note 9 –Leases in the Notes to Consolidated Financial Statements in our 2017 Annual Report for additional information relating to our lease obligations .

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events We have evaluated events that have occurred after June 30, 2018 through the issuance of these unaudited condensed consolidated financial statements. Any material subsequent events that occurred during this time have been properly recognized or disclosed in the unaudited condensed consolidated financial statements and accompanying notes. Distribution On July 25, 2018 , the Board declared a cash distribution of $0.365 per limited partner unit for the three months ended June 30, 2018 . The distribution will be paid on August 14, 2018 to unitholders of record as of August 6, 2018 . Credit Facility Agreements On July 31, 2018, we entered into a seven -year fixed rate credit facility with STCW with a borrowing capacity of $600.0 million (the “ Seven Year Fixed Facility”). We incurred an issuance fee of $1.3 million , which will be paid on or about August 7, 2018. The Seven Year Fixed Facility bears an interest rate of 4.06% per annum and matures on July 31, 2025. The Seven Year Fixed Facility contains customary representations, warranties, covenants and events of default, the occurrence of which would permit the lender to accelerate the maturity date of amounts borrowed under the Seven Year Fixed Facility. The Seven Year Fixed Facility was fully drawn on August 1, 2018 and the borrowings were used to partially repay borrowings under the Five Year Revolver due December 2022. On August 1, 2018, we amended and restated the Five Year Revolver due October 2019 such that the facility will now mature on July 31, 2023 (the “Five Year Revolver due July 2023”). The Five Year Revolver due July 2023 will still bear interest at LIBOR plus a margin. There is no issuance fee associated with this amendment. All other material terms and conditions of the Five Year Revolver due July 2023 remain unchanged.

Description of Business and B20

Description of Business and Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business We are a fee-based, growth-oriented master limited partnership that owns, operates, develops and acquires pipelines and other midstream assets. As of June 30, 2018 , our assets include interests in entities that own crude oil and refined products pipelines and terminals that serve as key infrastructure to (i) transport onshore and offshore crude oil production to Gulf Coast and Midwest refining markets and (ii) deliver refined products from those markets to major demand centers. Our assets also include interests in entities that own natural gas and refinery gas pipelines that transport offshore natural gas to market hubs and deliver refinery gas from refineries and plants to chemical sites along the Gulf Coast.
Basis of Presentation	Basis of Presentation Our unaudited condensed consolidated financial statements include all subsidiaries required to be consolidated under generally accepted accounting principles in the United States (“GAAP”). Our reporting currency is U.S. dollars, and all references to dollars are U.S. dollars. The accompanying unaudited condensed consolidated financial statements and related notes have been prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete annual financial statements. The year-end condensed consolidated balance sheet data was derived from audited financial statements. During interim periods, we follow the accounting policies disclosed in our Annual Report on Form 10-K for the year ended December 31, 2017 (our “2017 Annual Report”), filed with the United States Securities and Exchange Commission (“SEC”). The unaudited condensed consolidated financial statements for the three and six months ended June 30, 2018 and 2017 include all adjustments we believe are necessary for a fair statement of the results of operations for the interim periods presented. These adjustments are of a normal recurring nature unless otherwise disclosed. Operating results for the interim periods are not necessarily indicative of the results that may be expected for the full year. These unaudited condensed consolidated financial statements and other information included in this Quarterly Report on Form 10-Q should be read in conjunction with our audited consolidated financial statements and notes thereto included in our 2017 Annual Report. Our consolidated subsidiaries include Pecten, Sand Dollar, Triton, Zydeco, Odyssey and the Operating Company. Asset acquisitions of additional interests in previously consolidated subsidiaries and interests in cost and equity method investments are included in the financial statements prospectively from the effective date of each acquisition. In cases where these types of acquisitions are considered acquisitions of businesses under common control, the financial statements are retrospectively adjusted. As such, all financial results of interests acquired in the May 2017 Acquisition and the December 2017 Acquisition (as defined in Note 3—Acquisitions and Divestiture ) have been retrospectively adjusted. For additional common control interests acquired of cost and equity method investments previously owned, only the incremental ownership interest has been retrospectively adjusted. Our unaudited condensed consolidated financial statements were derived from the financial statements and accounting records of SPLC and Shell for the periods prior to acquisition. Specifically, such businesses are reflected for the following periods prior to the effective date of such acquisitions by us: • May 2017 Acquisition for periods prior to May 10, 2017; and • December 2017 Acquisition for periods prior to December 1, 2017, including the effect of fully consolidating Odyssey. Our unaudited condensed consolidated statements of income and cash flow for the periods ended June 30, 2017 consist of the combined results of the May 2017 Acquisition and the December 2017 Acquisition prior to the respective acquisition dates, and the consolidated activity of the Partnership. Our unaudited condensed consolidated statement of income excludes the results of these businesses from net income attributable to the Partnership for the periods indicated above by allocating these results to our Parent. See Note 3 - Acquisitions and Divestiture for definitions and additional information.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Standards Adopted as of January 1, 2018 In May 2014, the FASB issued Accounting Standards Update (“ASU”) 2014-09 to Topic 606, Revenue from Contracts with Customers, which superseded nearly all revenue recognition guidance in Topic 605, Revenue Recognition, under GAAP. We adopted the new standard utilizing the modified retrospective transition approach, effective January 1, 2018, by recognizing the cumulative effect of initially applying the standard for periods prior to January 1, 2018 to the opening balance of equity (deficit). See Note 2—Revenue Recognition for additional information and disclosures required by the new standard. In January 2017, the FASB issued ASU 2017-01 to Topic 805, Business Combinations, to clarify the definition of a business and to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This update was effective for us as of January 1, 2018. There was no impact on our financial statements as a result of this adoption in relation to our acquisition during the second quarter. In August 2016, the FASB issued ASU 2016-15 to Topic 230, Statement of Cash Flows, making changes to the classification of certain cash receipts and cash payments in order to reduce diversity in presentation. The update addresses eight specific cash flow issues, of which only one is applicable to our financial statements. The applicable update relates to distributions received from equity method investees and prescribes two options for presenting these cash flows: cumulative earnings approach or nature of the distribution approach. We will continue to apply the cumulative earnings approach, where distributions received are considered either returns on investment and classified as operating cash flows or returns of investment and classified as investing cash flows. The adoption of this update on January 1, 2018 did not have a material impact on our financial statements. In January 2016, the FASB issued ASU 2016-01 to Topic 825, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities, requiring equity investments (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. Additionally, the update allows equity investments that do not have readily determinable fair values to be re-measured at fair value either upon the occurrence of an observable price change or upon identification of impairment, and requires additional disclosure around those investments. We have the following three equity investments which are accounted for under the cost method and which do not have readily determinable fair values: June 30, 2018 December 31, 2017 Ownership Amount Ownership Amount Colonial 6.0 % $ 11.4 6.0 % $ 11.4 Explorer 12.62 % 48.6 12.62 % 48.6 Cleopatra 1.0 % 2.1 1.0 % 2.1 $ 62.1 $ 62.1 As of the adoption of this update on January 1, 2018, and as of June 30, 2018, we did not identify the occurrence of an observable price change or an identification of impairment for these three equity investments. Therefore, the adoption of this update on January 1, 2018 did not have a material impact on our financial statements. Standards Not Yet Adopted In February 2016, the FASB issued ASU 2016-02 to Topic 842, Leases, which requires lessees to recognize right-of-use assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either a financing lease or operating lease with classification affecting the pattern of expense recognition in the condensed consolidated statements of income and presentation of cash flows in the condensed consolidated statements of cash flows. This update also requires improved disclosures to help users of financial statements better understand the amount, timing and uncertainty of cash flows arising from leases. For lessors, this update modifies the classification criteria and the accounting for sales-type and direct financing leases. This update is effective on a modified retrospective basis for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. We will adopt the new standard on January 1, 2019 and continue to assess its impact to our consolidated financial statements and related disclosures. Currently, we plan to elect the practical expedients upon transition that will retain the lease classification and initial direct costs for any leases that exist prior to adoption. We will not reassess whether any contracts entered into prior to adoption are leases. In January 2018, the FASB issued ASU 2018-01 to provide an optional transition practical expedient to not evaluate existing or expired land easements that were not previously accounted for as leases under existing guidance. We intend to elect this practical expedient. In July 2018, the FASB issued ASU 2018-11 which provides entities an optional transitional relief method that allows entities to not apply the new guidance in the comparative periods they present in their financial statements in the year of adoption. This update also provides an optional practical expedient for lessors to avoid separating lease and associated non-lease components within a contract if certain criteria are met. We are evaluating this most recent update and continue to evaluate all other available transition practical expedients offered in connection with the new standard. As part of our implementation efforts to date, we have substantially completed the identification and aggregation of our lease contract population. We are reviewing these to determine the transition approach and assess the impact to our condensed consolidated financial statements upon adoption. We are also developing and starting to implement any necessary changes to existing processes and controls.

Description of Business and B21

Description of Business and Basis of Presentation (Tables)	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Ownership Percentage	The following table reflects our ownership, and Shell’s retained ownership as of June 30, 2018 : SHLX Ownership Shell’s Retained Ownership Pecten Midstream LLC (“Pecten”) 100.0 % — % Sand Dollar Pipeline LLC (“Sand Dollar”) 100.0 % — % Triton West LLC (“Triton”) 100.0 % — % Zydeco Pipeline Company LLC (“Zydeco”) 92.5 % 7.5 % Amberjack Pipeline Company LLC (“Amberjack”) – Series A/Series B 75.0% / 50.0% — % Mars Oil Pipeline Company LLC (“Mars”) 71.5 % — % Odyssey Pipeline L.L.C. (“Odyssey”) 71.0 % — % Bengal Pipeline Company LLC (“Bengal”) 50.0 % — % Crestwood Permian Basin LLC (“Permian Basin”) 50.0 % — % LOCAP LLC (“LOCAP”) 41.48 % — % Poseidon Oil Pipeline Company LLC (“Poseidon”) 36.0 % — % Explorer Pipeline Company (“Explorer”) 12.62 % 25.97 % Proteus Oil Pipeline Company, LLC (“Proteus”) 10.0 % — % Endymion Oil Pipeline Company, LLC (“Endymion”) 10.0 % — % Colonial Pipeline Company (“Colonial”) 6.0 % 10.12 % Cleopatra Gas Gathering Company, LLC (“Cleopatra”) 1.0 % — %
Schedule of Equity Investments in Affiliates	We have the following three equity investments which are accounted for under the cost method and which do not have readily determinable fair values: June 30, 2018 December 31, 2017 Ownership Amount Ownership Amount Colonial 6.0 % $ 11.4 6.0 % $ 11.4 Explorer 12.62 % 48.6 12.62 % 48.6 Cleopatra 1.0 % 2.1 1.0 % 2.1 $ 62.1 $ 62.1

Revenue Recognition (Tables)

Revenue Recognition (Tables)	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table provides information about disaggregated revenue by service type and customer type: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Transportation services revenue – third parties $ 54.7 $ 87.0 Transportation services revenue – related parties (1) 42.2 72.8 Total transportation services revenue 96.9 159.8 Storage services revenue – third parties 2.3 4.6 Storage services revenue – related parties 1.5 2.8 Total storage services revenue 3.8 7.4 Terminaling services revenue – third parties — — Terminaling services revenue – related parties 11.4 22.8 Total terminaling services revenue (2) 11.4 22.8 Product revenue – third parties 1.4 1.4 Product revenue – related parties 1.7 9.6 Total product revenue (3) 3.1 11.0 Total Topic 606 revenue 115.2 201.0 Lease revenue 14.1 27.9 Total revenue $ 129.3 $ 228.9 (1) Transportation services revenue - related parties for the three and six months ended June 30, 2018 includes $1.2 million and $2.4 million , respectively, of the non-lease service component in our transportation services contracts. (2) Terminaling services revenue is entirely comprised of the non-lease service component in our terminaling services contracts. (3) Product revenue is comprised of allowance oil sales.
Summary of the Impact of Adoption of the New Standard	In accordance with the new revenue standard, the following tables summarize the impact of adoption on our unaudited condensed consolidated financial statements as of and for the three and six months ended June 30, 2018 : Three Months Ended June 30, 2018 Unaudited Condensed Consolidated Statement of Income As Reported Under Topic 606 Amounts Without Adoption of Topic 606 Effect of Change Increase/(Decrease) Revenue Transportation, terminaling and storage services – third parties $ 57.0 $ 57.3 $ (0.3 ) Transportation, terminaling and storage services – related parties 55.1 43.7 11.4 Product revenue – third parties 1.4 — 1.4 Product revenue – related parties 1.7 — 1.7 Lease revenue – related parties 14.1 26.6 (12.5 ) Costs and expenses Cost of product sold – third parties 1.2 — 1.2 Cost of product sold – related parties 1.2 — 1.2 Operations and maintenance – third parties 24.9 25.7 (0.8 ) Operations and maintenance – related parties 13.3 11.6 1.7 Net income 115.4 116.7 (1.3 ) Six Months Ended June 30, 2018 Unaudited Condensed Consolidated Statement of Income As Reported Under Topic 606 Amounts Without Adoption of Topic 606 Effect of Change Increase/(Decrease) Revenue Transportation, terminaling and storage services – third parties $ 91.6 $ 90.9 $ 0.7 Transportation, terminaling and storage services – related parties 98.4 75.8 22.6 Product revenue – third parties 1.4 — 1.4 Product revenue – related parties 9.6 — 9.6 Lease revenue – related parties 27.9 53.0 (25.1 ) Costs and expenses Cost of product sold – third parties 1.2 — 1.2 Cost of product sold – related parties 7.7 — 7.7 Operations and maintenance – third parties 68.0 69.0 (1.0 ) Operations and maintenance – related parties 26.7 22.4 4.3 Net income 180.2 183.1 (2.9 ) June 30, 2018 Unaudited Condensed Consolidated Balance Sheet As Reported Under Topic 606 Amounts Without Adoption of Topic 606 Effect of Change Increase/(Decrease) Deferred revenue – related party $ 6.7 $ 8.3 $ (1.6 )
Contract Balances	The following table provides information about receivables and contract liabilities from contracts with customers: January 1, 2018 June 30, 2018 Receivables from contracts with customers – third parties $ 17.2 $ 19.7 Receivables from contracts with customers – related parties 18.8 17.3 Deferred revenue – third parties 5.5 4.8 Deferred revenue – related party 9.4 6.7 Significant changes in the deferred revenue balances with customers during the period are as follows: December 31, 2017 Transition Adjustment Additions (1) Reductions (2) June 30, 2018 Deferred revenue – third parties $ 5.5 — 3.4 (4.1 ) $ 4.8 Deferred revenue – related party $ 13.9 (4.5 ) 1.5 (4.2 ) $ 6.7 (1) Contract liability additions resulted from deficiency payments from minimum volume commitment contracts. (2) Contract liability reductions resulted from revenue earned through the actual or estimated use and expiration of deficiency credits.
Remaining Performance Obligations	The following table includes revenue expected to be recognized in the future related to performance obligations exceeding one year of their initial terms that are unsatisfied or partially unsatisfied as of June 30, 2018 : Total 2018 2019 2020 2021 2022 and beyond Revenue expected to be recognized on multi-year committed shipper transportation contracts in place as of June 30, 2018 (1) $ 642.0 $ 102.2 $ 64.3 $ 50.1 $ 49.8 $ 375.6 Revenue expected to be recognized on other multi-year transportation service contracts in place as of June 30, 2018 (2) 47.7 2.7 5.4 5.4 5.4 28.8 Revenue expected to be recognized on multi-year storage service contracts in place as of June 30, 2018 6.0 2.0 4.0 — — — Revenue expected to be recognized on multi-year terminaling service contracts in place as of June 30, 2018 (2) 430.0 22.8 45.7 45.7 45.7 270.1 $ 1,125.7 $ 129.7 $ 119.4 $ 101.2 $ 100.9 $ 674.5 (1) Excludes revenue deferred for deficiency payments. (2) Relates to the non-lease service components of certain of our long-term transportation and terminaling service contracts which are accounted for as operating leases.

Acquisitions and Divestitures (

Acquisitions and Divestitures (Tables)	6 Months Ended
	Jun. 30, 2018
Business Combinations [Abstract]
Schedule of Business Acquisitions	The results of the December 2017 Acquisition prior to the closing date of the acquisition are included in the acquisition column and the consolidated results are included in “Consolidated Results” within the tables below: Three Months Ended June 30, 2017 Shell Midstream Partners, L.P. (1) December 2017 Acquisition (2) Consolidated Results Revenue Transportation, terminaling and storage services – third parties $ 55.3 $ 4.4 $ 59.7 Transportation, terminaling and storage services – related parties 23.7 15.8 39.5 Lease revenue – related parties 7.8 5.4 13.2 Total revenue 86.8 25.6 112.4 Costs and expenses Operations and maintenance – third parties 22.9 3.6 26.5 Operations and maintenance – related parties 7.1 2.9 10.0 General and administrative – third parties 2.8 0.9 3.7 General and administrative – related parties 8.2 3.4 11.6 Depreciation, amortization and accretion 9.6 1.7 11.3 Property and other taxes 3.4 0.8 4.2 Total costs and expenses 54.0 13.3 67.3 Operating income 32.8 12.3 45.1 Income from equity method investments 37.2 7.5 44.7 Dividend income from cost investments 6.2 3.2 9.4 Investment and dividend income 43.4 10.7 54.1 Interest expense, net 7.5 — 7.5 Income before income taxes 68.7 23.0 91.7 Income tax expense — — — Net income 68.7 23.0 91.7 Less: Net income attributable to Parent 1.0 20.5 21.5 Less: Net income attributable to noncontrolling interests 2.2 2.5 4.7 Net income attributable to the Partnership $ 65.5 $ — $ 65.5 (1) As previously reported in our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2017, including the effect of retrospectively adjusting for the May 2017 Acquisition. (2) Our Parents’ results of the December 2017 Acquisition for the three months ended June 30, 2017. Six Months Ended June 30, 2017 Shell Midstream Partners, L.P. (1) December 2017 Acquisition (2) Consolidated Results Revenue Transportation, terminaling and storage services – third parties $ 110.8 $ 8.1 $ 118.9 Transportation, terminaling and storage services – related parties 52.6 31.3 83.9 Lease revenue – related parties 7.8 10.9 18.7 Total revenue 171.2 50.3 221.5 Costs and expenses Operations and maintenance – third parties 38.5 7.0 45.5 Operations and maintenance – related parties 18.2 5.5 23.7 General and administrative – third parties 4.6 1.1 5.7 General and administrative – related parties 16.6 7.1 23.7 Depreciation, amortization and accretion 19.1 3.5 22.6 Property and other taxes 7.6 1.5 9.1 Total costs and expenses 104.6 25.7 130.3 Operating income 66.6 24.6 91.2 Income from equity method investments 75.9 15.5 91.4 Dividend income from cost investments 13.5 6.0 19.5 Investment and dividend income 89.4 21.5 110.9 Interest expense, net 12.3 — 12.3 Income before income taxes 143.7 46.1 189.8 Income tax expense — — — Net income 143.7 46.1 189.8 Less: Net income attributable to Parent 3.0 41.0 44.0 Less: Net income attributable to noncontrolling interests 4.4 5.1 9.5 Net income attributable to the Partnership $ 136.3 $ — $ 136.3 (1) As previously reported in our Quarterly Report on Form 10-Q for the six months ended June 30, 2017, including the effect of retrospectively adjusting for the May 2017 Acquisition. (2) Our Parents’ results of the December 2017 Acquisition for the six months ended June 30, 2017. Six months Ended June 30, 2017 Shell Midstream Partners, L.P. (1) December 2017 Acquisition (2) Consolidated Results Cash flows from operating activities Net income $ 143.7 $ 46.1 $ 189.8 Adjustments to reconcile net income to net cash provided by operating activities Depreciation, amortization and accretion 19.1 3.5 22.6 Non-cash interest expense 0.1 — 0.1 Allowance oil reduction to net realizable value 0.3 — 0.3 Undistributed equity earnings (1.5 ) (2.7 ) (4.2 ) Changes in operating assets and liabilities Accounts receivable (14.2 ) (0.3 ) (14.5 ) Allowance oil 0.7 — 0.7 Prepaid expenses and other assets 1.8 0.1 1.9 Accounts payable 5.2 (0.6 ) 4.6 Deferred revenue and other unearned income 10.4 — 10.4 Accrued liabilities 9.7 (1.3 ) 8.4 Net cash provided by operating activities 175.3 44.8 220.1 Cash flows from investing activities Capital expenditures (20.9 ) (4.9 ) (25.8 ) Acquisitions from Parent (210.6 ) — (210.6 ) Purchase price adjustment 0.4 — 0.4 Return of investment 8.4 2.1 10.5 April 2017 Divestiture 0.8 — 0.8 Net cash used in investing activities (221.9 ) (2.8 ) (224.7 ) Cash flows from financing activities Net proceeds from public offerings 2.9 — 2.9 Borrowings under credit facility 580.0 — 580.0 Contributions from general partner 0.1 — 0.1 Proceeds from April 2017 Divestiture 20.2 — 20.2 Capital distributions to general partner (419.4 ) — (419.4 ) Distributions to noncontrolling interests (6.6 ) (5.1 ) (11.7 ) Distributions to unitholders and general partner (122.2 ) — (122.2 ) Net distributions to Parent (6.3 ) (36.9 ) (43.2 ) Other contributions from Parent 12.4 — 12.4 Credit facility issuance costs (0.7 ) — (0.7 ) Other (0.3 ) — (0.3 ) Net cash provided by (used in) financing activities 60.1 (42.0 ) 18.1 Net increase in cash and cash equivalents 13.5 — 13.5 Cash and cash equivalents at beginning of the period 121.9 0.2 122.1 Cash and cash equivalents at end of the period $ 135.4 $ 0.2 $ 135.6 Supplemental Cash Flow Information Non-cash investing and financing transactions Distribution of working capital to Parent $ (2.8 ) $ — $ (2.8 ) Change in accrued capital expenditures 2.7 (0.9 ) 1.8 Other non-cash contributions from Parent 1.1 — 1.1 (1) As previously reported in our Quarterly Report on Form 10-Q for the six months ended June 30, 2017, including the effect of retrospectively adjusting for the May 2017 Acquisition. (2) Our Parents’ results of the December 2017 Acquisition for the six months ended June 30, 2017.

Related Party Transactions (Tab

Related Party Transactions (Tables)	6 Months Ended
	Jun. 30, 2018
Related Party Transactions [Abstract]
Schedule of Other Related Party Balances	Other related party balances consist of the following: June 30, 2018 December 31, 2017 Accounts receivable $ 24.8 $ 23.8 Prepaid expenses 4.9 11.9 Other assets 2.6 1.7 Accounts payable (1) 12.6 11.6 Deferred revenue 6.7 13.9 Accrued liabilities (2) 11.5 7.2 Debt payable (3) 2,091.5 1,844.0 (1) Accounts payable reflects amounts owed to SPLC for reimbursement of third party expenses incurred by SPLC for our benefit. (2) As of June 30, 2018 , accrued liabilities reflects $ 11.0 million accrued interest and $ 0.5 million other accrued liabilities. As of December 31, 2017, accrued liabilities reflects $ 6.6 million accrued interest and $ 0.6 million other accrued liabilities. (3) Debt payable reflects borrowings outstanding after taking into account unamortized debt issuance costs of $2.5 million and $2.9 million as of June 30, 2018 and December 31, 2017 , respectively.
Schedule of Related Party Revenues	Related party revenues consist of the following: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Transportation and terminaling services revenue – related parties $ 53.6 $ 38.1 $ 95.6 $ 80.6 Product revenue – related parties 1.7 — 9.6 — Storage services revenue – related parties 1.5 1.4 2.8 3.3 Lease revenue – related parties 14.1 13.2 27.9 18.7 Total revenue – related parties $ 70.9 $ 52.7 $ 135.9 $ 102.6
Schedule of Future Minimum Payments To Be Received	As of June 30, 2018 , future minimum payments to be received under the ten -year contract term of these operating leases, which includes both the lease and non-lease service components of these leases, are estimated to be: Total Less than 1 year Years 2 to 3 Years 4 to 5 More than 5 years Operating leases $ 974.8 $ 106.4 $ 212.8 $ 212.8 $ 442.8
Schedule of Related Party Expenses Including Personnel Costs	The following table shows related party expenses, including personnel costs described above, incurred by Shell and SPLC on our behalf that are reflected in the accompanying unaudited condensed consolidated statements of income for the indicated periods: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Operations and maintenance – related parties $ 13.3 $ 10.0 $ 26.7 $ 23.7 General and administrative – related parties 13.9 11.6 26.8 23.7
Schedule of Reimbursements from Parent	The following table reflects reimbursements from our Parent for the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Cash received (1) $ 4.8 $ 6.8 $ 5.9 $ 9.4 Changes in receivable from Parent (2) (3.1 ) (2.7 ) 0.2 1.1 Total reimbursements (3) $ 1.7 $ 4.1 $ 6.1 $ 10.5 (1) These reimbursements are included in Other contributions from Parent in the accompanying consolidated statements of cash flows. (2) These reimbursements are included in Other non-cash contributions from Parent in the accompanying consolidated statements of cash flows. (3) These reimbursements are included in Other contributions from Parent in the accompanying consolidated statements of equity (deficit) and are exclusive of $1.6 million for the six months ended June 30, 2018 related to contributions from Parent.

Equity Method Investments (Tabl

Equity Method Investments (Tables)	6 Months Ended
	Jun. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Equity Investments in Affiliates	Equity method investments comprise the following as of the dates indicated: June 30, 2018 December 31, 2017 Ownership Investment Amount Ownership Investment Amount Amberjack – Series A / Series B 75.0% / 50.0% $ 465.7 —% $ — Mars 71.5% 168.9 71.5% 187.4 Bengal 50.0% 80.6 50.0% 79.7 Permian Basin 50.0% 61.5 50.0% 49.4 LOCAP 41.48% 8.4 41.48% 6.9 Poseidon 36.0% — 36.0% 2.3 Proteus 10.0% 16.8 10.0% 17.4 Endymion 10.0% 19.0 10.0% 19.5 $ 820.9 $ 362.6
Schedule of Equity Investments in Affiliates Balance Affected	Our equity method investments balance was affected by the following during the periods indicated: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Distributions Received Income from Equity Investments Distributions Received Income from Equity Investments Impact of Change in Accounting Policy Amberjack (1) $ 31.9 $ 16.0 $ 31.9 $ 16.0 $ — Mars 25.4 21.2 57.6 46.0 (6.9 ) Bengal 4.9 5.4 8.9 9.8 — Poseidon (2) 8.9 — 18.3 6.4 — Other (3) 6.3 5.8 11.8 10.4 — $ 77.4 $ 48.4 $ 128.5 $ 88.6 $ (6.9 ) (1) We acquired an interest in Amberjack in the May 2018 Acquisition. The acquisition of this interest has been accounted for prospectively. (2) As stated above, the equity method of accounting has been suspended for Poseidon and excess distributions are recorded as Other Income. (3) Included in Other is the activity associated with our investments in Permian Basin, LOCAP, Proteus and Endymion. We acquired a 50.0% interest in Permian Basin in October 2017 from a third party. The acquisition of this interest has been accounted for prospectively. Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 Distributions Received Income from Equity Investments Distributions Received Income from Equity Investments Purchase Price Adjustment Mars (1) $ 27.9 $ 29.7 $ 62.2 $ 61.3 $ — Bengal 4.6 5.4 9.3 10.7 — Poseidon 9.3 6.4 19.3 13.2 — Other (2) 5.3 3.2 6.9 6.2 (0.4 ) $ 47.1 $ 44.7 $ 97.7 $ 91.4 $ (0.4 ) (1) We acquired an additional 22.9% interest in Mars in the December 2017 Acquisition. The financial information presented for the three and six months ended June 30, 2017 has been retrospectively adjusted for the incremental ownership acquired. (2) Included in Other is the activity associated with our investments in LOCAP, Proteus and Endymion. We acquired a 41.48% interest in LOCAP in the December 2017 Acquisition. The financial information presented for the three and six months ended June 30, 2017 has been retrospectively adjusted for the ownership acquired.
Summary of Income Statement Data for Equity Method Investments	The following tables present aggregated selected unaudited income statement data for our equity method investments (on a 100% basis): Three Months Ended June 30, 2018 Total revenues Total operating expenses Operating income Net income Statements of Income Amberjack (1) $ 69.9 $ 17.5 $ 52.4 $ 52.5 Mars 51.8 21.3 30.5 30.5 Bengal 18.1 7.4 10.7 10.7 Poseidon 27.3 7.9 19.4 17.4 Other (2) 38.8 14.7 24.1 21.4 (1) Although our interest in Amberjack was acquired on May 11, 2018, the financial results for the full three months ended June 30, 2018 is presented for comparability. (2) Included in Other is the activity associated with our investments in Permian Basin, LOCAP, Proteus and Endymion. Six Months Ended June 30, 2018 Total revenues Total operating expenses Operating income Net income Statements of Income Amberjack (1) $ 132.0 $ 36.2 $ 95.8 $ 95.9 Mars 109.0 43.0 66.0 66.0 Bengal 33.5 14.2 19.3 19.3 Poseidon 56.2 16.5 39.7 36.0 Other (2) 75.4 30.2 45.2 40.2 (1) Although our interest in Amberjack was acquired on May 11, 2018, the financial results for the full six months ended June 30, 2018 is presented for comparability. (2) Included in Other is the activity associated with our investments in Permian Basin, LOCAP, Proteus and Endymion. Three Months Ended June 30, 2017 Total revenues Total operating expenses Operating income Net income Statements of Income Mars $ 66.4 $ 24.3 $ 42.1 $ 42.1 Bengal 18.1 7.1 11.0 10.9 Poseidon 28.5 8.5 20.0 18.6 Other (1) 29.8 10.2 19.6 14.7 (1) Included in Other is the activity associated with our investments in LOCAP, Proteus and Endymion. Six Months Ended June 30, 2017 Total revenues Total operating expenses Operating income Net income Statements of Income Mars $ 131.3 $ 44.2 $ 87.1 $ 87.1 Bengal 35.9 14.3 21.6 21.5 Poseidon 57.4 16.6 40.8 38.0 Other (1) 58.8 20.0 38.8 29.8 (1) Included in Other is the activity associated with our investments in LOCAP, Proteus and Endymion.

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	6 Months Ended
	Jun. 30, 2018
Property, Plant and Equipment [Abstract]
Components of Property, Plant and Equipment	Property, plant and equipment consist of the following as of the dates indicated: Depreciable Life June 30, 2018 December 31, 2017 Land — $ 8.2 $ 8.2 Building and improvements 10 - 40 years 38.9 38.9 Pipeline and equipment (1) 10 - 30 years 1,155.8 1,153.6 Other 5 - 25 years 17.8 17.8 1,220.7 1,218.5 Accumulated depreciation and amortization (2) (548.5 ) (526.1 ) 672.2 692.4 Construction in progress 69.0 44.1 Property, plant and equipment, net $ 741.2 $ 736.5 (1) As of June 30, 2018 and December 31, 2017, includes cost of $357.9 million and $353.7 million , respectively, related to assets under operating lease (as lessor), which commenced in May 2017 and December 2017. As of both June 30, 2018 and December 31, 2017, includes cost of $22.8 million related to assets under capital lease (as lessee). (2) As of June 30, 2018 and December 31, 2017, includes accumulated depreciation of $111.2 million and $104.7 million , respectively, related to assets under operating lease (as lessor), which commenced in May 2017 and December 2017. As of June 30, 2018 and December 31, 2017, includes accumulated depreciation of $3.7 million and $3.0 million , respectively, related to assets under capital lease (as lessee).

Accrued Liabilities - Third P27

Accrued Liabilities - Third Parties (Tables)	6 Months Ended
	Jun. 30, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities – third parties consist of the following as of the dates indicated: June 30, 2018 December 31, 2017 Transportation, project engineering $ 15.1 $ 6.0 Property taxes 9.2 4.2 Other accrued liabilities 2.2 2.5 Total accrued liabilities – third parties $ 26.5 $ 12.7

Related Party Debt (Tables)

Related Party Debt (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Schedule of Consolidated Related Party Debt Obligations	Consolidated related party debt obligations comprise the following as of the dates indicated: June 30, 2018 December 31, 2017 Outstanding Balance Total Capacity Available Capacity Outstanding Balance Total Capacity Available Capacity Five Year Revolver due December 2022 $ 1,000.0 $ 1,000.0 $ — $ 1,000.0 $ 1,000.0 $ — Five Year Fixed Facility 600.0 600.0 — 600.0 600.0 — Five Year Revolver due October 2019 (1) 494.0 760.0 266.0 246.9 760.0 513.1 Zydeco Revolver — 30.0 30.0 — 30.0 30.0 Unamortized debt issuance costs (2.5 ) n/a n/a (2.9 ) n/a n/a Debt payable – related party $ 2,091.5 $ 2,390.0 $ 296.0 $ 1,844.0 $ 2,390.0 $ 543.1 (1) On August 1, 2018, the Partnership extended the maturity date. See Note 13 – Subsequent Events for additional information.

Equity (Deficit) (Tables)

Equity (Deficit) (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Schedule of Changes in Number of Units Outstanding	The changes in the number of units outstanding from December 31, 2017 through June 30, 2018 are as follows: Public SPLC General (in units) Common Common Partner Total Balance as of December 31, 2017 98,832,233 88,950,136 3,832,293 191,614,662 Units issued in connection with equity offerings 25,000,000 11,029,412 735,295 36,764,707 Balance as of June 30, 2018 123,832,233 99,979,548 4,567,588 228,379,369
Schedule of Distributions Declared and/or Paid	The following table details the distributions declared and/or paid for the periods presented: Date Paid or Public SPLC SPLC General Partner Distributions to be Paid Three Months Ended Common Common Subordinated IDR's 2% Total (in millions, except per unit amounts) February 14, 2017 December 31, 2016 $ 24.5 $ 5.9 $ 18.7 $ 8.3 $ 1.2 $ 58.6 $ 0.27700 May 12, 2017 March 31, 2017 25.7 25.9 — 10.7 1.3 63.6 0.29100 August 14, 2017 June 30, 2017 26.9 27.0 — 12.9 1.4 68.2 0.30410 November 14, 2017 September 30, 2017 31.4 28.3 — 16.2 1.5 77.4 0.31800 February 14, 2018 December 31, 2017 32.9 29.6 — 18.9 1.7 83.1 0.33300 May 15, 2018 March 31, 2018 43.1 34.8 — 25.7 2.1 105.7 0.34800 August 14, 2018 June 30, 2018 (1) 45.2 36.5 — 29.4 2.3 113.4 0.36500 (1) For more information see Note 13 — Subsequent Events .

Net Income Per Limited Partne30

Net Income Per Limited Partner Unit (Tables)	6 Months Ended
	Jun. 30, 2018
Partners' Capital Notes [Abstract]
Schedule of Allocation of Net Income Attributable to the Partnership to Arrive at Net Income Per Limited Partner Unit	The following tables show the allocation of net income attributable to the Partnership to arrive at net income per limited partner unit: Three Months Ended Six Months Ended 2018 2017 2018 2017 Net income $ 115.4 $ 91.7 $ 180.2 $ 189.8 Less: Net income attributable to Parent — 21.5 — 44.0 Net income attributable to noncontrolling interests 4.7 4.7 5.5 9.5 Net income attributable to the Partnership 110.7 65.5 174.7 136.3 Less: General Partner’s distribution declared 31.7 14.3 59.5 26.3 Limited Partners’ distribution declared on common units 81.7 53.9 159.6 105.5 Income (less than) / in excess of distributions $ (2.7 ) $ (2.7 ) $ (44.4 ) $ 4.5
Schedule of Basic and Diluted Net Income Per Unit	Three Months Ended June 30, 2018 General Partner Limited Partners ’ Common Units Total (in millions of dollars, except per unit data) Distributions declared $ 31.7 $ 81.7 $ 113.4 Distributions in excess of income (0.1 ) (2.6 ) (2.7 ) Net income attributable to the Partnership $ 31.6 $ 79.1 $ 110.7 Weighted average units outstanding (in millions): Basic and diluted 223.8 Net income per Limited Partner Unit (in dollars): Basic and diluted $ 0.35 Six Months Ended June 30, 2018 General Partner Limited Partners ’ Common Units Total (in millions of dollars, except per unit data) Distributions declared $ 59.5 $ 159.6 $ 219.1 Distributions in excess of income (0.9 ) (43.5 ) (44.4 ) Net income attributable to the Partnership $ 58.6 $ 116.1 $ 174.7 Weighted average units outstanding (in millions): Basic and diluted 216.7 Net income per Limited Partner Unit (in dollars): Basic and diluted $ 0.54 Three Months Ended June 30, 2017 General Partner Limited Partners ’ Common Units Total (in millions of dollars, except per unit data) Distributions declared $ 14.3 $ 53.9 $ 68.2 Income in excess of distributions — (2.7 ) (2.7 ) Net income attributable to the Partnership $ 14.3 $ 51.2 $ 65.5 Weighted average units outstanding (in millions) (1) : Basic and diluted 177.4 Net income per Limited Partner Unit (in dollars): Basic and diluted $ 0.29 Six Months Ended June 30, 2017 General Partner Limited Partners ’ Common Units Total (in millions of dollars, except per unit data) Distributions declared $ 26.3 $ 105.5 $ 131.8 Income in excess of distributions 0.1 4.4 4.5 Net income attributable to the Partnership $ 26.4 $ 109.9 $ 136.3 Weighted average units outstanding (in millions) (1) : Basic and diluted 177.3 Net income per Limited Partner Unit (in dollars): Basic and diluted $ 0.62 (1) The subordinated units converted into common units on February 15, 2017 and were considered outstanding common units for the entire period with respect to the weighted average number of units outstanding.

Description of Business and B31

Description of Business and Basis of Presentation (Details) - segment	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Description Of Business And Basis Of Presentation [Line Items]
Number of reportable segments	1
Pecten Midstream LLC (“Pecten”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	100.00%
Shell’s Retained Ownership	0.00%
Sand Dollar Pipeline LLC (“Sand Dollar”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	100.00%
Shell’s Retained Ownership	0.00%
Triton West LLC (“Triton”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	100.00%
Shell’s Retained Ownership	0.00%
Zydeco Pipeline Company LLC (“Zydeco”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	92.50%
Shell’s Retained Ownership	7.50%
Amberjack Pipeline Company LLC (“Amberjack”) - Series A
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	75.00%
Shell’s Retained Ownership	0.00%
Amberjack Pipeline Company LLC (“Amberjack”) - Series B
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	50.00%
Shell’s Retained Ownership	0.00%
Mars Oil Pipeline Company LLC (“Mars”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	71.50%	71.50%
Shell’s Retained Ownership	0.00%
Odyssey Pipeline L.L.C. (“Odyssey”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	71.00%
Shell’s Retained Ownership	0.00%
Bengal Pipeline Company LLC (“Bengal”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	50.00%	50.00%
Shell’s Retained Ownership	0.00%
Crestwood Permian Basin LLC (“Permian Basin”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	50.00%	50.00%
Shell’s Retained Ownership	0.00%
LOCAP LLC (“LOCAP”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	41.48%	41.48%
Shell’s Retained Ownership	0.00%
Poseidon Oil Pipeline Company LLC (“Poseidon”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	36.00%	36.00%
Shell’s Retained Ownership	0.00%
Explorer Pipeline Company (“Explorer”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	12.62%
Shell’s Retained Ownership	25.97%
Proteus Oil Pipeline Company, LLC (“Proteus”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	10.00%	10.00%
Shell’s Retained Ownership	0.00%
Endymion Oil Pipeline Company, LLC (“Endymion”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	10.00%	10.00%
Shell’s Retained Ownership	0.00%
Colonial Pipeline Company (“Colonial”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	6.00%
Shell’s Retained Ownership	10.12%
Cleopatra Gas Gathering Company, LLC (“Cleopatra”)
Description Of Business And Basis Of Presentation [Line Items]
SHLX Ownership	1.00%
Shell’s Retained Ownership	0.00%

Description of Business and B32

Description of Business and Basis of Presentation - Equity Method Investments (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Investment Amount	$ 62.1	$ 62.1
Colonial
Schedule of Equity Method Investments [Line Items]
Ownership	6.00%	6.00%
Investment Amount	$ 11.4	$ 11.4
Explorer
Schedule of Equity Method Investments [Line Items]
Ownership	12.62%	12.62%
Investment Amount	$ 48.6	$ 48.6
Cleopatra
Schedule of Equity Method Investments [Line Items]
Ownership	1.00%	1.00%
Investment Amount	$ 2.1	$ 2.1

Revenue Recognition (Details)

Revenue Recognition (Details) - Effect of Change Increase/(Decrease) - Accounting Standards Update 2014-09 $ in Millions	Dec. 31, 2017USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect to total equity (deficit)	$ 4.5
Mars
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect to total equity (deficit)	$ (2.3)

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregated Revenue (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	$ 115.2			$ 201
Lease revenue	14.1	$ 13.2		27.9	$ 18.7
Total revenue	129.3	112.4	[1]	228.9	221.5	[1]
Transportation Services
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	96.9			159.8
Transportation Services | Third Parties
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	54.7			87
Transportation Services | Related Parties
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	42.2			72.8
Storage Services
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	3.8			7.4
Storage Services | Third Parties
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	2.3			4.6
Storage Services | Related Parties
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	1.5			2.8
Terminaling Services
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	11.4			22.8
Terminaling Services | Third Parties
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	0			0
Terminaling Services | Related Parties
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	11.4			22.8
Product Revenue
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	3.1			11
Product Revenue | Third Parties
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	1.4	0	[1]	1.4	0	[1]
Product Revenue | Related Parties
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	1.7	$ 0	[1]	9.6	$ 0	[1]
Transportation Services, Non-lease Service | Related Parties
Disaggregation of Revenue [Line Items]
Total Topic 606 revenue	$ 1.2			$ 2.4
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Revenue Recognition - Impact of

Revenue Recognition - Impact of Adoption (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017		Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	$ 115.2			$ 201
Lease revenue – related parties	14.1	$ 13.2	[1]	27.9	$ 18.7	[1]
Cost of product sold – third parties	1.2	0		1.2	0
Cost of product sold – related parties	1.2	0	[1]	7.7	0	[1]
Operations and maintenance – third parties	24.9	26.5	[1]	68	45.5	[1]
Operations and maintenance – related parties	13.3	10	[1]	26.7	23.7	[1]
Deferred revenue – related party	6.7			6.7			$ 13.9
Net income	115.4	91.7	[1]	180.2	189.8	[1],[2]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	115.5	91.7	[1]	180.3	189.8	[1]
Amounts Without Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Lease revenue – related parties	26.6
Cost of product sold – third parties	0			0
Cost of product sold – related parties	0			0
Operations and maintenance – third parties	25.7			69
Operations and maintenance – related parties	11.6			22.4
Deferred revenue – related party	8.3			8.3
Net income	116.7			183.1
Effect of Change Increase/(Decrease) | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Lease revenue – related parties	(12.5)
Cost of product sold – third parties	1.2			1.2
Cost of product sold – related parties	1.2			7.7
Operations and maintenance – third parties	(0.8)			(1)
Operations and maintenance – related parties	1.7			4.3
Deferred revenue – related party	(1.6)			(1.6)
Net income	(1.3)			(2.9)
Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	3.1			11
Third Parties | Transportation, Terminaling and Storage Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	57	59.7	[1]	91.6	118.9	[1]
Third Parties | Transportation, Terminaling and Storage Services | Amounts Without Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	57.3			90.9
Third Parties | Transportation, Terminaling and Storage Services | Effect of Change Increase/(Decrease) | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	(0.3)			0.7
Third Parties | Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	1.4	0	[1]	1.4	0	[1]
Third Parties | Product Revenue | Amounts Without Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	0			0
Third Parties | Product Revenue | Effect of Change Increase/(Decrease) | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	1.4			1.4
Related Parties | Transportation, Terminaling and Storage Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	55.1	39.5	[1]	98.4	83.9	[1]
Related Parties | Transportation, Terminaling and Storage Services | Amounts Without Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	43.7			75.8
Related Parties | Transportation, Terminaling and Storage Services | Effect of Change Increase/(Decrease) | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	11.4			22.6
Related Parties | Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	1.7	$ 0	[1]	9.6	$ 0	[1]
Related Parties | Product Revenue | Amounts Without Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	0			0
Related Parties | Product Revenue | Effect of Change Increase/(Decrease) | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	$ 1.7			9.6
Related Parties | Lease Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer				27.9
Related Parties | Lease Revenue | Amounts Without Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer				53
Related Parties | Lease Revenue | Effect of Change Increase/(Decrease) | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer				$ (25.1)
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.
[2]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Revenue Recognition - Contract

Revenue Recognition - Contract Balances (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Receivables from contracts with customers		$ 19.8		$ 17.2
Deferred revenue	$ 4.8	4.8	$ 5.5
Movement in Deferred Revenue [Roll Forward]
Deferred revenue, ending balance	4.8
Third Parties
Disaggregation of Revenue [Line Items]
Receivables from contracts with customers		19.7	17.2
Deferred revenue	5.5	4.8		5.5
Movement in Deferred Revenue [Roll Forward]
Deferred revenue, beginning balance	5.5
Transition Adjustment	0
Additions	3.4
Reductions	(4.1)
Deferred revenue, ending balance	4.8
Related Parties
Disaggregation of Revenue [Line Items]
Receivables from contracts with customers		17.3	18.8
Deferred revenue	13.9	$ 6.7	$ 9.4	$ 13.9
Movement in Deferred Revenue [Roll Forward]
Deferred revenue, beginning balance	13.9
Transition Adjustment	(4.5)
Additions	1.5
Reductions	(4.2)
Deferred revenue, ending balance	$ 6.7

Revenue Recognition - Remaining

Revenue Recognition - Remaining Performance Obligations (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 129.7
Revenue, remaining performance obligation, expected timing of satisfaction, period	6 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 119.4
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 101.2
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 100.9
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 674.5
Revenue, remaining performance obligation, expected timing of satisfaction, period
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 1,125.7
Revenue expected to be recognized on multi-year committed shipper transportation contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	102.2
Revenue expected to be recognized on multi-year committed shipper transportation contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	64.3
Revenue expected to be recognized on multi-year committed shipper transportation contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	50.1
Revenue expected to be recognized on multi-year committed shipper transportation contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	49.8
Revenue expected to be recognized on multi-year committed shipper transportation contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	375.6
Revenue expected to be recognized on multi-year committed shipper transportation contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	642
Revenue expected to be recognized on other multi-year transportation service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	2.7
Revenue expected to be recognized on other multi-year transportation service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	5.4
Revenue expected to be recognized on other multi-year transportation service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	5.4
Revenue expected to be recognized on other multi-year transportation service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	5.4
Revenue expected to be recognized on other multi-year transportation service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	28.8
Revenue expected to be recognized on other multi-year transportation service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	47.7
Revenue expected to be recognized on multi-year storage service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	2
Revenue expected to be recognized on multi-year storage service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	4
Revenue expected to be recognized on multi-year storage service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	0
Revenue expected to be recognized on multi-year storage service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	0
Revenue expected to be recognized on multi-year storage service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	0
Revenue expected to be recognized on multi-year storage service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	6
Revenue expected to be recognized on multi-year terminaling service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	22.8
Revenue expected to be recognized on multi-year terminaling service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	45.7
Revenue expected to be recognized on multi-year terminaling service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	45.7
Revenue expected to be recognized on multi-year terminaling service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	45.7
Revenue expected to be recognized on multi-year terminaling service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	270.1
Revenue expected to be recognized on multi-year terminaling service contracts in place as of June 30, 2018 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 430

Acquisitions and Divestiture (D

Acquisitions and Divestiture (Details) - USD ($) $ in Millions		May 11, 2018	Dec. 01, 2017	May 10, 2017	Apr. 28, 2017	Nov. 03, 2014	Mar. 31, 2018	Jun. 30, 2018	Jun. 30, 2017
Business Acquisition [Line Items]
April 2017 Divestiture	[1]							$ 0	$ 0.8
Zydeco | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
April 2017 Divestiture					$ 21
Book value of net assets divested					0.8
Excess proceeds received from Parent					20.2
Shell Pipeline Company L P | Zydeco | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
April 2017 Divestiture					$ 19.4
Shell Treasury Center West Inc | Five Year Revolver
Business Acquisition [Line Items]
Debt instrument term								5 years
Shell Treasury Center West Inc | Five Year Fixed Facility
Business Acquisition [Line Items]
Debt instrument term								5 years
Five Year Revolver due October 2019 (1)
Business Acquisition [Line Items]
Debt instrument term						5 years
Five Year Revolver due December 2022
Business Acquisition [Line Items]
Debt instrument term							5 years
Five Year Fixed Facility
Business Acquisition [Line Items]
Debt instrument term							5 years
Amberjack - Series A
Business Acquisition [Line Items]
Interest acquired		75.00%
Amberjack - Series B
Business Acquisition [Line Items]
Interest acquired		50.00%
May 2018 Acquisition
Business Acquisition [Line Items]
Consideration transferred		$ 1,220
Historical carrying value of net assets under common control		481.6
Consideration in excess of the historical carrying value of net assets under common control		738.4
May 2018 Acquisition | Five Year Revolver due October 2019 (1)
Business Acquisition [Line Items]
Consideration transferred		494
May 2018 Acquisition | Five Year Revolver due October 2019 (1) | Shell Treasury Center West Inc
Business Acquisition [Line Items]
Debt instrument term				5 years
May 2018 Acquisition | Five Year Revolver due December 2022
Business Acquisition [Line Items]
Consideration transferred		$ 726
May 2018 Acquisition | Five Year Fixed Facility | Shell Treasury Center West Inc
Business Acquisition [Line Items]
Debt instrument term				5 years
Triton West LLC (“Triton”)
Business Acquisition [Line Items]
Interest acquired			100.00%
LOCAP
Business Acquisition [Line Items]
Interest acquired			41.48%
Mars
Business Acquisition [Line Items]
Interest acquired			22.90%
Odyssey
Business Acquisition [Line Items]
Interest acquired			22.00%
Explorer Pipeline Company
Business Acquisition [Line Items]
Interest acquired			10.00%
December 2017 Acquisition
Business Acquisition [Line Items]
Consideration transferred			$ 825
December 2017 Acquisition | Five Year Revolver due December 2022
Business Acquisition [Line Items]
Debt instrument term			5 years
Delta Pipeline
Business Acquisition [Line Items]
Interest acquired				100.00%
Na Kika
Business Acquisition [Line Items]
Interest acquired				100.00%
Refinery Gas Pipeline
Business Acquisition [Line Items]
Interest acquired				100.00%
May 2017 Acquisition
Business Acquisition [Line Items]
Interest acquired				100.00%
Consideration transferred				$ 630
Consideration, cash on hand				50
May 2017 Acquisition | Five Year Revolver due October 2019 (1) | Shell Treasury Center West Inc | Five Year Revolver
Business Acquisition [Line Items]
Consideration, funded with borrowings				73.1
May 2017 Acquisition | Five Year Fixed Facility | Shell Treasury Center West Inc
Business Acquisition [Line Items]
Consideration, funded with borrowings				$ 506.9
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Acquisitions and Divestiture -

Acquisitions and Divestiture - Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Revenue
Total Topic 606 revenue	$ 115.2			$ 201
Lease revenue – related parties	14.1	$ 13.2		27.9	$ 18.7
Total revenue	129.3	112.4	[1]	228.9	221.5	[1]
Costs and expenses
Operations and maintenance – third parties	24.9	26.5	[1]	68	45.5	[1]
Operations and maintenance – related parties	13.3	10	[1]	26.7	23.7	[1]
General and administrative – third parties	2.2	3.7	[1]	4.1	5.7	[1]
General and administrative – related parties	13.9	11.6	[1]	26.8	23.7	[1]
Depreciation, amortization and accretion	11.4	11.3	[1],[2]	22.8	22.6	[1],[2]
Property and other taxes	4.5	4.2	[1]	10	9.1	[1]
Total costs and expenses	72.6	67.3	[1]	167.3	130.3	[1]
Operating income	56.7	45.1	[1]	61.6	91.2	[1]
Income from equity method investments	48.4	44.7	[1]	88.6	91.4	[1]
Dividend income from cost investments	12.8	9.4	[1]	37.7	19.5	[1]
Investment, dividend and other income	72.1	54.1	[1]	142.6	110.9	[1]
Interest expense, net	13.3	7.5	[1]	23.9	12.3	[1]
Income before income taxes	115.5	91.7	[1]	180.3	189.8	[1]
Income tax expense	0.1	0	[1]	0.1	0	[1]
Net income	115.4	91.7	[1]	180.2	189.8	[1],[2]
Less: Net income attributable to Parent	0	21.5	[1]	0	44	[1]
Less: Net income attributable to noncontrolling interests	4.7	4.7	[1]	5.5	9.5	[1]
Net income attributable to the Partnership	110.7	65.5	[1]	174.7	136.3	[1]
Previously Reported
Revenue
Lease revenue – related parties		7.8			7.8
Total revenue		86.8			171.2
Costs and expenses
Operations and maintenance – third parties		22.9			38.5
Operations and maintenance – related parties		7.1			18.2
General and administrative – third parties		2.8			4.6
General and administrative – related parties		8.2			16.6
Depreciation, amortization and accretion		9.6			19.1
Property and other taxes		3.4			7.6
Total costs and expenses		54			104.6
Operating income		32.8			66.6
Income from equity method investments		37.2			75.9
Dividend income from cost investments		6.2			13.5
Investment, dividend and other income		43.4			89.4
Interest expense, net		7.5			12.3
Income before income taxes		68.7			143.7
Income tax expense		0			0
Net income		68.7			143.7
Less: Net income attributable to Parent		1			3
Less: Net income attributable to noncontrolling interests		2.2			4.4
Net income attributable to the Partnership		65.5			136.3
December 2017 Acquisition | Previously Reported
Revenue
Lease revenue – related parties		5.4			10.9
Total revenue		25.6			50.3
Costs and expenses
Operations and maintenance – third parties		3.6			7
Operations and maintenance – related parties		2.9			5.5
General and administrative – third parties		0.9			1.1
General and administrative – related parties		3.4			7.1
Depreciation, amortization and accretion		1.7			3.5
Property and other taxes		0.8			1.5
Total costs and expenses		13.3			25.7
Operating income		12.3			24.6
Income from equity method investments		7.5			15.5
Dividend income from cost investments		3.2			6
Investment, dividend and other income		10.7			21.5
Interest expense, net		0			0
Income before income taxes		23			46.1
Income tax expense		0			0
Net income		23			46.1
Less: Net income attributable to Parent		20.5			41
Less: Net income attributable to noncontrolling interests		2.5			5.1
Net income attributable to the Partnership		0			0
Third Parties | Transportation, Terminaling and Storage Services
Revenue
Total Topic 606 revenue	57	59.7	[1]	91.6	118.9	[1]
Third Parties | Transportation, Terminaling and Storage Services | Previously Reported
Revenue
Total Topic 606 revenue		55.3			110.8
Third Parties | Transportation, Terminaling and Storage Services | December 2017 Acquisition | Previously Reported
Revenue
Total Topic 606 revenue		4.4			8.1
Related Parties | Transportation, Terminaling and Storage Services
Revenue
Total Topic 606 revenue	$ 55.1	39.5	[1]	$ 98.4	83.9	[1]
Related Parties | Transportation, Terminaling and Storage Services | Previously Reported
Revenue
Total Topic 606 revenue		23.7			52.6
Related Parties | Transportation, Terminaling and Storage Services | December 2017 Acquisition | Previously Reported
Revenue
Total Topic 606 revenue		$ 15.8			$ 31.3
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.
[2]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Acquisitions and Divestiture 40

Acquisitions and Divestiture - Statement of Cash Flows (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net income		$ 115.4	$ 91.7	[1]	$ 180.2	$ 189.8	[1],[2]
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, amortization and accretion		11.4	11.3	[1],[2]	22.8	22.6	[1],[2]
Non-cash interest expense					0.4	0.1	[2]
Allowance oil reduction to net realizable value					0	0.3	[2]
Undistributed equity earnings					(2.2)	(4.2)	[2]
Changes in operating assets and liabilities
Accounts receivable					(3.5)	(14.5)	[2]
Allowance oil					(6.5)	0.7	[2]
Prepaid expenses and other assets					6.4	1.9	[2]
Accounts payable					1.3	4.6	[2]
Deferred revenue and other unearned income					(3.3)	10.4	[2]
Accrued liabilities					17.6	8.4	[2]
Net cash provided by operating activities					213.2	220.1	[2]
Cash flows from investing activities
Capital expenditures					(25.1)	(25.8)	[2]
Acquisitions from Parent	[2]				(481.6)	(210.6)
Purchase price adjustment					0	0.4	[2]
Return of investment					32.6	10.5	[2]
April 2017 Divestiture	[2]				0	0.8
Net cash used in investing activities					(488.1)	(224.7)	[2]
Cash flows from financing activities
Net proceeds from equity offerings					973.3	2.9	[2]
Borrowings under credit facilities	[2]				1,220	580
Contributions from general partner					20	0.1	[2]
Proceeds from April 2017 Divestiture					0	20.2	[2]
Capital distributions to general partner	[2]				(738.4)	(419.4)
Capital distributions to general partner					0	(43.2)	[2]
Distributions to noncontrolling interests					(6.6)	(11.7)	[2]
Distributions to unitholders and general partner					(188.8)	(122.2)	[2]
Other contributions from Parent					5.9	12.4	[2]
Credit facility issuance costs					0	(0.7)	[2]
Other					(0.4)	(0.3)	[2]
Net cash provided by financing activities					312.1	18.1	[2]
Net increase in cash and cash equivalents					37.2	13.5	[2]
Cash and cash equivalents at beginning of the period					137.7	122.1	[2]
Cash and cash equivalents at end of the period		$ 174.9	135.6	[2]	174.9	135.6	[2]
Distribution of working capital to Parent					0	(2.8)	[2]
Change in accrued capital expenditures					0.5	1.8	[2]
Other non-cash contributions from Parent					$ 1.9	1.1	[2]
Previously Reported
Cash flows from operating activities
Net income			68.7			143.7
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, amortization and accretion			9.6			19.1
Non-cash interest expense						0.1
Allowance oil reduction to net realizable value						0.3
Undistributed equity earnings						(1.5)
Changes in operating assets and liabilities
Accounts receivable						(14.2)
Allowance oil						0.7
Prepaid expenses and other assets						1.8
Accounts payable						5.2
Deferred revenue and other unearned income						10.4
Accrued liabilities						9.7
Net cash provided by operating activities						175.3
Cash flows from investing activities
Capital expenditures						(20.9)
Acquisitions from Parent						(210.6)
Purchase price adjustment						0.4
Return of investment						8.4
April 2017 Divestiture						0.8
Net cash used in investing activities						(221.9)
Cash flows from financing activities
Net proceeds from equity offerings						2.9
Borrowings under credit facilities						580
Contributions from general partner						0.1
Proceeds from April 2017 Divestiture						20.2
Capital distributions to general partner						(419.4)
Capital distributions to general partner						(6.3)
Distributions to noncontrolling interests						(6.6)
Distributions to unitholders and general partner						(122.2)
Other contributions from Parent						12.4
Credit facility issuance costs						(0.7)
Other						(0.3)
Net cash provided by financing activities						60.1
Net increase in cash and cash equivalents						13.5
Cash and cash equivalents at beginning of the period						121.9
Cash and cash equivalents at end of the period			135.4			135.4
Distribution of working capital to Parent						(2.8)
Change in accrued capital expenditures						2.7
Other non-cash contributions from Parent						1.1
December 2017 Acquisition | Previously Reported
Cash flows from operating activities
Net income			23			46.1
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, amortization and accretion			1.7			3.5
Non-cash interest expense						0
Allowance oil reduction to net realizable value						0
Undistributed equity earnings						(2.7)
Changes in operating assets and liabilities
Accounts receivable						(0.3)
Allowance oil						0
Prepaid expenses and other assets						0.1
Accounts payable						(0.6)
Deferred revenue and other unearned income						0
Accrued liabilities						(1.3)
Net cash provided by operating activities						44.8
Cash flows from investing activities
Capital expenditures						(4.9)
Acquisitions from Parent						0
Purchase price adjustment						0
Return of investment						2.1
April 2017 Divestiture						0
Net cash used in investing activities						(2.8)
Cash flows from financing activities
Net proceeds from equity offerings						0
Borrowings under credit facilities						0
Contributions from general partner						0
Proceeds from April 2017 Divestiture						0
Capital distributions to general partner						0
Capital distributions to general partner						(36.9)
Distributions to noncontrolling interests						(5.1)
Distributions to unitholders and general partner						0
Other contributions from Parent						0
Credit facility issuance costs						0
Other						0
Net cash provided by financing activities						(42)
Net increase in cash and cash equivalents						0
Cash and cash equivalents at beginning of the period						0.2
Cash and cash equivalents at end of the period			$ 0.2			0.2
Distribution of working capital to Parent						0
Change in accrued capital expenditures						(0.9)
Other non-cash contributions from Parent						$ 0
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.
[2]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) $ in Millions	Nov. 03, 2014USD ($)	Jun. 30, 2018USD ($)credit_facility	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)credit_facilityterm	Jun. 30, 2017USD ($)	Dec. 31, 2017
Related Party Transaction [Line Items]
Statute of limitations expirations, number of days	60 days
Revenue from related parties		$ 70.9	$ 52.7	$ 135.9	$ 102.6
Health and life insurance costs		1.7	1.5	3.3	3.1
Defined contribution benefit plan costs		0.7	0.6	1.3	1.2
Reimbursement of cost and expenses		1.7	4.1	$ 6.1	10.5
Transportation Services Operating Leases
Related Party Transaction [Line Items]
Initial term				10 years
Transportation Services Operating Leases, Five Year Terms
Related Party Transaction [Line Items]
Initial term				10 years
Number of additional terms | term				2
Additional term				5 years
Transportation Services Operating Leases, One Year Terms
Related Party Transaction [Line Items]
Initial term				10 years
Number of additional terms | term				10
Additional term				1 year
Management Agreement
Related Party Transaction [Line Items]
Payment for general administrative services		2.2	2	$ 4.3	4
Omnibus Agreement
Related Party Transaction [Line Items]
Payment for general administrative services		2.1	2.1	4.2	4.2
Zydeco Pipeline Company LLC (“Zydeco”)
Related Party Transaction [Line Items]
Reimbursement of cost and expenses		3.5		9.9
Shell Pipeline Company L P
Related Party Transaction [Line Items]
Reimbursement of cost and expenses		$ 1.7	4.1	$ 6.1	10.5
Shell Treasury Center West Inc
Related Party Transaction [Line Items]
Number of revolving credit facilities | credit_facility		3		3
SPLC
Related Party Transaction [Line Items]
General insurance expense		$ 3.7	1.4	$ 7.3	3.4
Operations and maintenance costs allocated from parent		3	3.4	7.4	7.6
General and administrative - related parties		$ 8.3	6.3	15.9	$ 13.5
Refinery Gas Pipeline
Related Party Transaction [Line Items]
Reimbursement of cost and expenses			$ 0.6	$ 0.6
Five Year Revolver | Shell Treasury Center West Inc
Related Party Transaction [Line Items]
Debt instrument term				5 years
Five Year Fixed Facility | Shell Treasury Center West Inc
Related Party Transaction [Line Items]
Debt instrument term				5 years
Shell Pipeline Company L P
Related Party Transaction [Line Items]
Payment of general and administrative fee	$ 8.5
Zydeco Pipeline Company LLC (“Zydeco”)
Related Party Transaction [Line Items]
Noncontrolling interest		7.50%		7.50%		7.50%
Odyssey
Related Party Transaction [Line Items]
Noncontrolling interest		29.00%		29.00%		29.00%

Related Party Transactions - Sc

Related Party Transactions - Schedule of Other Related Party Balances (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Accounts receivable	$ 24.8	$ 23.8
Prepaid expenses	4.9	11.9
Other assets	2.6	1.7
Accounts payable	12.6	11.6
Deferred revenue	6.7	13.9
Accrued liabilities	11.5	7.2
Debt payable	2,091.5	1,844
Accrued interest, related parties	11	6.6
Other accrued liabilities, related parties	0.5	0.6
Unamortized debt issuance costs	2.5	2.9
Affiliated Entity
Related Party Transaction [Line Items]
Unamortized debt issuance costs	$ 2.5	$ 2.9

Related Party Transactions - Re

Related Party Transactions - Related Party Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Related Party Transaction [Line Items]
Lease revenue – related parties	$ 14.1	$ 13.2	$ 27.9	$ 18.7
Revenue from related parties	70.9	52.7	135.9	102.6
Transportation and Terminaling Services
Related Party Transaction [Line Items]
Revenue from related parties	53.6	38.1	95.6	80.6
Product Revenue
Related Party Transaction [Line Items]
Revenue from related parties	1.7	0	9.6	0
Storage Services
Related Party Transaction [Line Items]
Revenue from related parties	$ 1.5	$ 1.4	$ 2.8	$ 3.3

Related Party Transactions - Fu

Related Party Transactions - Future Minimum Payments Receivable (Details) $ in Millions	Jun. 30, 2018USD ($)
Related Party Transactions [Abstract]
Total	$ 974.8
Less than 1 year	106.4
Years 2 to 3	212.8
Years 4 to 5	212.8
More than 5 years	$ 442.8

Related Party Transactions - 45

Related Party Transactions - Schedule of Condensed Combined Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	[1]	Jun. 30, 2018	Jun. 30, 2017	[1]
Related Party Transactions [Abstract]
Operations and maintenance – related parties	$ 13.3	$ 10		$ 26.7	$ 23.7
General and administrative – related parties	$ 13.9	$ 11.6		$ 26.8	$ 23.7
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Related Party Transactions - 46

Related Party Transactions - Reimbursements from Our General Partner (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Related Party Transaction [Line Items]
Changes in receivable from Parent			$ 1.9	$ 1.1	[1]
Reimbursement of cost and expenses	$ 1.7	$ 4.1	6.1	10.5
Contributions from Parent			7.7
Shell Pipeline Company L P
Related Party Transaction [Line Items]
Cash received	4.8	6.8	5.9	9.4
Changes in receivable from Parent	(3.1)	(2.7)	0.2	1.1
Reimbursement of cost and expenses	$ 1.7	$ 4.1	6.1	$ 10.5
Contributions from Parent			$ 1.6
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Equity Method Investments - Sch

Equity Method Investments - Schedule of Equity Investments in Affiliates (Details) - USD ($)	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Investment Amount	$ 820,900,000		$ 362,600,000
Amberjack – Series A / Series B
Schedule of Equity Method Investments [Line Items]
Ownership			0.00%
Investment Amount	$ 465,700,000		$ 0
Amberjack - Series A
Schedule of Equity Method Investments [Line Items]
Ownership	75.00%
Amberjack - Series B
Schedule of Equity Method Investments [Line Items]
Ownership	50.00%
Mars
Schedule of Equity Method Investments [Line Items]
Ownership	71.50%		71.50%
Investment Amount	$ 168,900,000		$ 187,400,000
Bengal
Schedule of Equity Method Investments [Line Items]
Ownership	50.00%		50.00%
Investment Amount	$ 80,600,000		$ 79,700,000
Crestwood Permian Basin LLC (“Permian Basin”)
Schedule of Equity Method Investments [Line Items]
Ownership	50.00%		50.00%
Investment Amount	$ 61,500,000		$ 49,400,000
LOCAP
Schedule of Equity Method Investments [Line Items]
Ownership	41.48%		41.48%
Investment Amount	$ 8,400,000		$ 6,900,000
Poseidon
Schedule of Equity Method Investments [Line Items]
Ownership	36.00%		36.00%
Investment Amount	$ 0	$ 0	$ 2,300,000
Proteus
Schedule of Equity Method Investments [Line Items]
Ownership	10.00%		10.00%
Investment Amount	$ 16,800,000		$ 17,400,000
Endymion
Schedule of Equity Method Investments [Line Items]
Ownership	10.00%		10.00%
Investment Amount	$ 19,000,000		$ 19,500,000

Equity Method Investments - Add

Equity Method Investments - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Dec. 01, 2017	Oct. 17, 2017
Schedule of Equity Method Investments [Line Items]
Unamortized basis differences included in equity investments	$ 42,200,000		$ 42,200,000			$ 41,400,000
Amortization expense (income)	900,000	$ 900,000	1,900,000	$ 1,900,000
Equity method investments	$ 820,900,000		$ 820,900,000			362,600,000
Cumulative effect to total (deficit)/equity						2,300,000
Mars
Schedule of Equity Method Investments [Line Items]
Interest acquired							22.90%
LOCAP
Schedule of Equity Method Investments [Line Items]
Interest acquired							41.48%
Odyssey
Schedule of Equity Method Investments [Line Items]
Interest acquired							22.00%
Permian Basin
Schedule of Equity Method Investments [Line Items]
Interest acquired								50.00%
Supermajority vote percentage	75.00%		75.00%
Capital contribution	$ 14,000,000
Accounting Standards Update 2016-01
Schedule of Equity Method Investments [Line Items]
Cumulative effect to total (deficit)/equity						6,900,000
Poseidon
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 0		$ 0		$ 0	$ 2,300,000

Equity Method Investments - S49

Equity Method Investments - Schedule of Equity Investments in Affiliates Balance Affected (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017		Dec. 31, 2017	Dec. 01, 2017	Oct. 17, 2017
Schedule of Equity Method Investments [Line Items]
Distributions Received	$ 77.4	$ 47.1		$ 128.5	$ 97.7
Income from equity method investments	48.4	44.7	[1]	88.6	91.4	[1]
Impact of Change in Accounting Policy							$ (6.9)
Purchase Price Adjustment				0	(0.4)	[2]
Amberjack (1)
Schedule of Equity Method Investments [Line Items]
Distributions Received	31.9			31.9
Income from equity method investments	16			16
Impact of Change in Accounting Policy							0
Mars
Schedule of Equity Method Investments [Line Items]
Distributions Received	25.4	27.9		57.6	62.2
Income from equity method investments	21.2	29.7		46	61.3
Impact of Change in Accounting Policy							(6.9)
Purchase Price Adjustment					0
Bengal
Schedule of Equity Method Investments [Line Items]
Distributions Received	4.9	4.6		8.9	9.3
Income from equity method investments	5.4	5.4		9.8	10.7
Impact of Change in Accounting Policy							0
Purchase Price Adjustment					0
Poseidon
Schedule of Equity Method Investments [Line Items]
Distributions Received	8.9	9.3		18.3	19.3
Income from equity method investments	0	6.4		6.4	13.2
Impact of Change in Accounting Policy							0
Purchase Price Adjustment					0
Other
Schedule of Equity Method Investments [Line Items]
Distributions Received	6.3	5.3		11.8	6.9
Income from equity method investments	$ 5.8	$ 3.2		$ 10.4	6.2
Impact of Change in Accounting Policy							$ 0
Purchase Price Adjustment					$ (0.4)
Mars
Schedule of Equity Method Investments [Line Items]
Interest acquired								22.90%
Permian Basin
Schedule of Equity Method Investments [Line Items]
Interest acquired									50.00%
LOCAP
Schedule of Equity Method Investments [Line Items]
Interest acquired								41.48%
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.
[2]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Equity Method Investments - Sum

Equity Method Investments - Summary of Income Statement Data for Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Amberjack (1)
Schedule of Equity Method Investments [Line Items]
Total Revenues	$ 69.9		$ 132
Total Operating Expenses	17.5		36.2
Operating Income	52.4		95.8
Net Income	52.5		95.9
Mars
Schedule of Equity Method Investments [Line Items]
Total Revenues	51.8	$ 66.4	109	$ 131.3
Total Operating Expenses	21.3	24.3	43	44.2
Operating Income	30.5	42.1	66	87.1
Net Income	30.5	42.1	66	87.1
Bengal
Schedule of Equity Method Investments [Line Items]
Total Revenues	18.1	18.1	33.5	35.9
Total Operating Expenses	7.4	7.1	14.2	14.3
Operating Income	10.7	11	19.3	21.6
Net Income	10.7	10.9	19.3	21.5
Poseidon
Schedule of Equity Method Investments [Line Items]
Total Revenues	27.3	28.5	56.2	57.4
Total Operating Expenses	7.9	8.5	16.5	16.6
Operating Income	19.4	20	39.7	40.8
Net Income	17.4	18.6	36	38
Proteus
Schedule of Equity Method Investments [Line Items]
Total Revenues	38.8	29.8	75.4	58.8
Total Operating Expenses	14.7	10.2	30.2	20
Operating Income	24.1	19.6	45.2	38.8
Net Income	$ 21.4	$ 14.7	$ 40.2	$ 29.8

Property, Plant and Equipment -

Property, Plant and Equipment - Components of Property, Plant and Equipment (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	[1],[2]	Jun. 30, 2018	Jun. 30, 2017	[1],[2]	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Land	$ 8.2			$ 8.2			$ 8.2
Building and improvements	38.9			38.9			38.9
Pipeline and equipment	1,155.8			1,155.8			1,153.6
Other	17.8			17.8			17.8
Property, plant and equipment, gross	1,220.7			1,220.7			1,218.5
Accumulated depreciation and amortization	(548.5)			(548.5)			(526.1)
Property plant and equipment excluding construction in progress	672.2			672.2			692.4
Construction in progress	69			69			44.1
Property, plant and equipment, net	741.2			741.2			736.5
Operating leased assets, cost	357.9			357.9			353.7
Costs related to assets under capital lease	22.8			22.8
Accumulated depreciation on assets under operating lease	111.2			111.2			104.7
Accumulated depreciation on assets under capital lease	3.7			3.7			$ 3
Depreciation and amortization expense	$ 11.4	$ 11.3		22.8	$ 22.6
Interest capitalized				$ 0.2
Building and Improvements | Minimum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life				10 years
Building and Improvements | Maximum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life				40 years
Pipeline and Equipment | Minimum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life				10 years
Pipeline and Equipment | Maximum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life				30 years
Other | Minimum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life				5 years
Other | Maximum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life				25 years
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.
[2]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Accrued Liabilities - Third P52

Accrued Liabilities - Third Parties - Schedule of Accrued Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Transportation, project engineering	$ 15.1	$ 6
Property taxes	9.2	4.2
Other accrued liabilities	2.2	2.5
Total accrued liabilities – third parties	$ 26.5	$ 12.7

Related Party Debt - Schedule o

Related Party Debt - Schedule of Consolidated Related Party Debt Obligations (Details) - USD ($) $ in Millions	Nov. 03, 2014	Mar. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Line Of Credit Facility [Line Items]
Outstanding Balance			$ 2,091.5	$ 1,844
Unamortized debt issuance costs			(2.5)	(2.9)
Total Capacity			2,390	2,390
Available Capacity			296	543.1
Five Year Revolver due December 2022
Line Of Credit Facility [Line Items]
Debt instrument term		5 years
Outstanding Balance			1,000	1,000
Total Capacity			1,000	1,000
Available Capacity			0	0
Five Year Fixed Facility
Line Of Credit Facility [Line Items]
Debt instrument term		5 years
Outstanding Balance			600	600
Total Capacity			600	600
Available Capacity			0	0
Five Year Revolver due October 2019 (1)
Line Of Credit Facility [Line Items]
Debt instrument term	5 years
Outstanding Balance			494	246.9
Total Capacity			760	760
Available Capacity			266	513.1
Zydeco Revolver
Line Of Credit Facility [Line Items]
Outstanding Balance			0	0
Total Capacity			30	30
Available Capacity			$ 30	$ 30

Related Party Debt - Additional

Related Party Debt - Additional Information (Details) - USD ($)

May 11, 2018

Feb. 06, 2018

May 10, 2017

Mar. 01, 2017

Nov. 03, 2014

Jun. 30, 2018

Mar. 31, 2018

Jun. 30, 2017

Jun. 30, 2018

Jun. 30, 2017

Dec. 31, 2017

Line Of Credit Facility [Line Items]

Interest and fee expenses

$ 12,900,000

$ 6,700,000

$ 22,900,000

$ 10,700,000

Interest paid

7,400,000

$ 4,000,000

18,500,000

7,700,000

Borrowing capacity

2,390,000,000

2,390,000,000

$ 2,390,000,000

Repayments of debt

972,900,000

$ 0

[1]

Level 2

Line Of Credit Facility [Line Items]

Long-term debt, carrying value

2,094,000,000

2,094,000,000

1,846,900,000

Long-term debt, fair value

2,088,500,000

2,088,500,000

1,858,400,000

Five Year Fixed Facility

Line Of Credit Facility [Line Items]

Borrowing capacity

600,000,000

600,000,000

600,000,000

Debt instrument term

5 years

Five Year Revolver due December 2022

Line Of Credit Facility [Line Items]

Borrowing capacity

1,000,000,000

1,000,000,000

1,000,000,000

Debt instrument term

5 years

Repayments of debt

$ 726,000,000

Five Year Revolver due October 2019 (1)

Line Of Credit Facility [Line Items]

Borrowing capacity

$ 760,000,000

$ 760,000,000

$ 760,000,000

Debt instrument term

5 years

Repayments of debt

$ 246,900,000

May 2018 Acquisition

Line Of Credit Facility [Line Items]

Consideration transferred

$ 1,220,000,000

May 2018 Acquisition | Five Year Revolver due December 2022

Line Of Credit Facility [Line Items]

Consideration transferred

726,000,000

May 2018 Acquisition | Five Year Revolver due October 2019 (1)

Line Of Credit Facility [Line Items]

Consideration transferred

$ 494,000,000

May 2018 Acquisition | Shell Treasury Center West Inc | Five Year Fixed Facility

Line Of Credit Facility [Line Items]

Debt instrument term

5 years

May 2018 Acquisition | Shell Treasury Center West Inc | Five Year Revolver due October 2019 (1)

Line Of Credit Facility [Line Items]

Debt instrument term

5 years

Five Year Fixed Facility | Shell Treasury Center West Inc

Line Of Credit Facility [Line Items]

Debt instrument term

5 years

Five Year Fixed Facility | Shell Treasury Center West Inc | Fixed Facility

Line Of Credit Facility [Line Items]

Debt instrument term

5 years

Five Year Fixed Facility | Shell Treasury Center West Inc | Fixed Facility | STCW

Line Of Credit Facility [Line Items]

Borrowing capacity

$ 600,000,000

[1]

(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Equity (Deficit) (Details)

Equity (Deficit) (Details)	Feb. 06, 2018USD ($)$ / sharesshares	Feb. 15, 2017shares	Mar. 02, 2016USD ($)	Jun. 30, 2018USD ($)shares	Jun. 30, 2017USD ($)$ / sharesshares	Jun. 30, 2018USD ($)shares	Jun. 30, 2017USD ($)$ / shares		Dec. 31, 2017shares
Class of Stock [Line Items]
Aggregate percentage of general partner interest						2.00%
Issuance of common units, maximum proceeds			$ 300,000,000
Units issued in connection with public offering (in shares) | shares						36,764,707
Net proceeds from equity offerings						$ 973,300,000
Contribution from general partner for additional shares issued	$ 13,900,000
Net proceeds from equity offerings						973,300,000	$ 2,900,000	[1]
Consideration for units issued to our general partner						$ 20,000,000	$ 100,000	[1]
Common unitholders' capital account, units outstanding (in shares) | shares				223,811,781		223,811,781
Ownership interest percentage						43.80%
Capital units, publicly owned (in shares) | shares				228,379,369		228,379,369			191,614,662
Five Year Revolver due October 2019 (1)
Class of Stock [Line Items]
Repayments of debt						$ 246,900,000
Debt instrument term						5 years
Five Year Revolver due December 2022
Class of Stock [Line Items]
Repayments of debt						$ 726,000,000
Debt instrument term						5 years
General Partner
Class of Stock [Line Items]
Aggregate percentage of general partner interest						2.00%
Units issued in connection with public offering (in shares) | shares	510,204					735,295
Units issued under the ATM Program (in shares) | shares	225,091				1,938
Consideration for units issued to our general partner					$ 100,000
Capital units, publicly owned (in shares) | shares				4,567,588		4,567,588			3,832,293
Common Units
Class of Stock [Line Items]
Common units per share (in USD per share) | $ / shares	$ 27.20
Units issued under the ATM Program (in shares) | shares	11,029,412
Net proceeds from equity offerings	$ 300,000,000
Consideration for units issued to our general partner	$ 6,100,000
Shell Pipeline Company L P | General Partner
Class of Stock [Line Items]
Aggregate percentage of general partner interest	2.00%					2.00%
Shell Pipeline Company L P | Limited Partner
Class of Stock [Line Items]
Aggregate percentage of general partner interest						98.00%
Shell Pipeline Company L P | Common Units
Class of Stock [Line Items]
Units issued in connection with public offering (in shares) | shares						11,029,412
Common unitholders' capital account, units outstanding (in shares) | shares				99,979,548		99,979,548			88,950,136
Capital units, publicly owned (in shares) | shares				99,979,548		99,979,548			88,950,136
General Public | Common Units
Class of Stock [Line Items]
Units issued in connection with public offering (in shares) | shares	25,000,000					25,000,000
Net proceeds from equity offerings	$ 673,300,000
Gross proceeds from public offering	$ 680,000,000
Common units per share (in USD per share) | $ / shares	$ 27.20				$ 31.51		$ 31.51
Underwriter fees	$ 6,000,000
Transaction fees	$ 700,000				$ 100,000
Units issued under the ATM Program (in shares) | shares					94,925
Common unitholders' capital account, units outstanding (in shares) | shares				123,832,233		123,832,233			98,832,233
Capital units, publicly owned (in shares) | shares				123,832,233		123,832,233			98,832,233
Partners' Capital Account, Private Placement of Units					$ 2,900,000
Gross Proceeds From Issuance Of Private Placement					3,000,000
Zydeco
Class of Stock [Line Items]
Distributions to noncontrolling interest				$ 2,900,000	3,400,000		$ 6,600,000
Odyssey
Class of Stock [Line Items]
Distributions to noncontrolling interest				$ 1,800,000	$ 2,600,000	$ 3,700,000	$ 5,100,000
Common Unitholders
Class of Stock [Line Items]
Shares converted (in shares) | shares		67,475,068
Conversion ratio (in common shares per subordinated shares)		1
May 2016 Acquisition | Shell Pipeline Company L P | General Partner
Class of Stock [Line Items]
Aggregate percentage of general partner interest					2.00%
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Equity (Deficit) - Schedule of

Equity (Deficit) - Schedule of Number of Units Outstanding (Details) - shares	Feb. 06, 2018	Jun. 30, 2018
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in shares)		191,614,662
Units issued in connection with equity offerings (in shares)		36,764,707
Ending balance (in shares)		228,379,369
General Partner
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in shares)		3,832,293
Units issued in connection with equity offerings (in shares)	510,204	735,295
Ending balance (in shares)		4,567,588
General Public | Common Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in shares)		98,832,233
Units issued in connection with equity offerings (in shares)	25,000,000	25,000,000
Ending balance (in shares)		123,832,233
Shell Pipeline Company L P | Common Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in shares)		88,950,136
Units issued in connection with equity offerings (in shares)		11,029,412
Ending balance (in shares)		99,979,548

Equity (Deficit) - Schedule o57

Equity (Deficit) - Schedule of Distributions Declared and/or Paid (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 06, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017		Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2018	Jun. 30, 2017	[1]
Distribution Made To Limited Partner [Line Items]
Aggregate percentage of general partner interest										2.00%
Distributions declared and/or paid		$ 113.4	$ 105.7	$ 83.1	$ 77.4	$ 68.2		$ 63.6	$ 58.6
Distributions paid per limited partner unit (in dollars per share)		$ 0.365	$ 0.348	$ 0.333	$ 0.3180	$ 0.30410	[1]	$ 0.291	$ 0.27700	$ 0.713	$ 0.5951
Common Units | General Public
Distribution Made To Limited Partner [Line Items]
Distributions declared and/or paid		$ 45.2	$ 43.1	$ 32.9	$ 31.4	$ 26.9		$ 25.7	$ 24.5
Common Units | Shell Pipeline Company L P
Distribution Made To Limited Partner [Line Items]
Distributions declared and/or paid		36.5	34.8	29.6	28.3	27		25.9	5.9
Subordinated Units | Shell Pipeline Company L P
Distribution Made To Limited Partner [Line Items]
Distributions declared and/or paid		0	0	0	0	0		0	18.7
General Partner
Distribution Made To Limited Partner [Line Items]
Aggregate percentage of general partner interest										2.00%
Distributions declared and/or paid		2.3	2.1	1.7	1.5	1.4		1.3	1.2
General Partner | Shell Pipeline Company L P
Distribution Made To Limited Partner [Line Items]
Aggregate percentage of general partner interest	2.00%									2.00%
General Partner | IDR's
Distribution Made To Limited Partner [Line Items]
Distributions declared and/or paid		$ 29.4	$ 25.7	$ 18.9	$ 16.2	$ 12.9		$ 10.7	$ 8.3
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Net Income Per Limited Partne58

Net Income Per Limited Partner Unit - Schedule of Allocation of Net Income to Arrive at Net Income Per Limited Partner Unit (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Limited Partners Capital Account [Line Items]
Net income	$ 115.4	$ 91.7	[1]	$ 180.2	$ 189.8	[1],[2]
Less: Net income attributable to Parent	0	21.5	[1]	0	44	[1]
Less: Net income attributable to noncontrolling interests	4.7	4.7	[1]	5.5	9.5	[1]
Net income attributable to the Partnership	110.7	65.5	[1]	174.7	136.3	[1]
Distributions declared	113.4	68.2		219.1	131.8
Income (less than) / in excess of distributions	(2.7)	(2.7)		(44.4)	4.5
General Partner
Limited Partners Capital Account [Line Items]
Net income attributable to the Partnership	31.6	14.3		58.6	26.4
Distributions declared	31.7	14.3		59.5	26.3
Income (less than) / in excess of distributions	(0.1)	0		(0.9)	0.1
Limited Partners’ Common Units
Limited Partners Capital Account [Line Items]
Net income attributable to the Partnership	79.1	51.2		116.1	109.9
Distributions declared	81.7	53.9		159.6	105.5
Income (less than) / in excess of distributions	$ (2.6)	$ (2.7)		$ (43.5)	$ 4.4
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.
[2]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Net Income Per Limited Partne59

Net Income Per Limited Partner Unit - Schedule of Basic and Diluted Net Income Per Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Distribution Made To Limited Partner [Line Items]
Distributions declared	$ 113.4	$ 68.2		$ 219.1	$ 131.8
Income (less than) / in excess of distributions	(2.7)	(2.7)		(44.4)	4.5
Net income attributable to the Partnership	110.7	65.5	[1]	174.7	136.3	[1]
General Partner
Distribution Made To Limited Partner [Line Items]
Distributions declared	31.7	14.3		59.5	26.3
Income (less than) / in excess of distributions	(0.1)	0		(0.9)	0.1
Net income attributable to the Partnership	31.6	14.3		58.6	26.4
Limited Partners’ Common Units
Distribution Made To Limited Partner [Line Items]
Distributions declared	81.7	53.9		159.6	105.5
Income (less than) / in excess of distributions	(2.6)	(2.7)		(43.5)	4.4
Net income attributable to the Partnership	$ 79.1	$ 51.2		$ 116.1	$ 109.9
Weighted average units outstanding (in millions)
Weighted average units outstanding, basic and diluted (in shares)	223.8	177.4		216.7	177.3
Net income per Limited Partner Unit (in dollars)
Net income per Limited Partner unit, basic and diluted (in dollars per share)	$ 0.35	$ 0.29	[1]	$ 0.54	$ 0.62	[1]
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Income Taxes Income Taxes (Deta

Income Taxes Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income tax expense	$ 0.1	$ 0	[1]	$ 0.1	$ 0	[1]
[1]	(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Millions	Jul. 01, 2018	Sep. 01, 2016	Jun. 30, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Environmental accrual			$ 0.3	$ 0.3
Tariff monthly payment		$ 0.4
Initial term		10 years
Renewal term		1 year
Subsequent Event
Other Commitments [Line Items]
Tariff rate increase	4.40%

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions

Jul. 31, 2018

Jul. 25, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

[1]

Mar. 31, 2017

Dec. 31, 2016

Jun. 30, 2018

Jun. 30, 2017

[1]

Subsequent Event [Line Items]

Distributions paid per limited partner unit (in dollars per share)

$ 0.365

$ 0.348

$ 0.333

$ 0.3180

$ 0.30410

$ 0.291

$ 0.27700

$ 0.713

$ 0.5951

Borrowing capacity

$ 2,390

$ 2,390

$ 2,390

Five Year Revolver due December 2022

Subsequent Event [Line Items]

Debt instrument term

5 years

Subsequent Event

Subsequent Event [Line Items]

Distributions paid per limited partner unit (in dollars per share)

$ 0.365

Subsequent Event | Five Year Revolver due December 2022 | Fixed Facility

Subsequent Event [Line Items]

Debt instrument term

5 years

Subsequent Event | Shell Treasury Center West Inc | Seven Year Fixed Facility Due July 2025 | Fixed Facility

Subsequent Event [Line Items]

Debt instrument term

7 years

Borrowing capacity

$ 600

Issuance fee incurred

$ 1.3

Debt instrument, interest rate

4.06%

[1]

(1) The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.