BP Midstream Partners (BPMP) 10-Q 12 Nov 19 2019 Q3 Quarterly report Financial data

Cover

Cover - shares	9 Months Ended
	Sep. 30, 2019	Nov. 11, 2019
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-38260
Entity Registrant Name	BP Midstream Partners LP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-1646447
Entity Address, Address Line One	501 Westlake Park Boulevard
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77079
City Area Code	281
Local Phone Number	366-2000
Title of 12(b) Security	Common Units, Representing Limited Partner Interests
Trading Symbol	BPMP
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001708301
Common Units
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		52,387,740
Subordinated Units
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		52,375,535

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 92,405	$ 56,970
Accounts receivable – third parties	491	325
Accounts receivable – related parties	10,843	9,769
Prepaid expenses	103	4,667
Other current assets	3,207	629
Total current assets	107,049	72,360
Equity method investments (Note 4)	537,575	549,039
Property, plant and equipment, net (Note 5)	64,866	68,580
Other assets	3,621	3,224
Total assets	713,111	693,203
Current liabilities
Accounts payable – third parties	556	607
Accounts payable – related parties	1,696	2,553
Deferred revenue and credits	3,026	1,067
Other current liabilities (Note 6)	6,747	6,900
Total current liabilities	12,025	11,127
Long-term debt (Note 7)	468,000	468,000
Other liabilities	3,567	3,224
Total liabilities	483,592	482,351
Commitments and contingencies (Note 12)
EQUITY
General partner	743	0
Total partner's capital	91,444	69,878
Non-controlling interests	138,075	140,974
Total equity	229,519	210,852
Total liabilities and equity	713,111	693,203
Common Units | Public
EQUITY
Common stock	846,386	836,789
Common Units | BP Holdco
EQUITY
Common stock	(60,781)	(61,684)
Subordinated Units | BP Holdco
EQUITY
Common stock	$ (694,904)	$ (705,227)

CONSOLIDATED BALANCE SHEEETS (P

CONSOLIDATED BALANCE SHEEETS (Parenthetical) - shares	Sep. 30, 2019	Dec. 31, 2018
Public | Common Units
Units outstanding (in shares)	47,806,563	47,802,826
Units issued (in shares)	47,806,563	47,802,826
BP Holdco | Common Units
Units outstanding (in shares)	4,581,177	4,581,177
Units issued (in shares)	4,581,177	4,581,177
BP Holdco | Subordinated Units
Units outstanding (in shares)	52,375,535	52,375,535
Units issued (in shares)	52,375,535	52,375,535

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands, shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue
Third parties	$ 725	$ 508	$ 2,238	$ 2,072
Related parties	33,836	31,566	91,164	85,556
Total revenue	34,561	32,074	93,402	87,628
Costs and expenses
Operating expenses – third parties	3,907	2,877	10,615	8,513
Operating expenses – related parties	1,423	1,506	4,317	3,494
Maintenance expenses – related parties	66	31	139	75
General and administrative – third parties	529	1,596	1,959	2,799
General and administrative – related parties	3,476	3,691	10,597	10,556
Lease expense	17	15	53	45
Depreciation	656	663	1,970	1,987
Impairment and other, net	0	0	1,000	0
Property and other taxes	111	165	361	388
Total costs and expenses	10,488	11,184	32,197	29,380
Operating income	24,073	20,890	61,205	58,248
Income from equity method investments	30,104	22,581	83,312	66,262
Interest expense (income), net	3,784	(20)	11,310	119
Income before income taxes	50,393	43,491	133,207	124,391
Income tax expense	0	0	0	0
Net income	50,393	43,491	133,207	124,391
Less: Net income attributable to non-controlling interests	4,639	8,272	12,969	28,163
Net income attributable to the Partnership	45,754	35,219	120,238	96,228
Limited Partners Common Units
Costs and expenses
Net income attributable to the Partnership	$ 22,508	$ 17,609	$ 59,453	$ 48,114
Net income attributable to the Partnership per limited partner unit – basic and diluted (in dollars):
Net income attributable to the Partnership per limited partner unit – basic and diluted (in dollars per share)	$ 0.43	$ 0.34	$ 1.13	$ 0.92
Limited Partners Subordinated Units
Costs and expenses
Net income attributable to the Partnership	$ 22,503	$ 17,610	$ 59,441	$ 48,114
Net income attributable to the Partnership per limited partner unit – basic and diluted (in dollars):
Net income attributable to the Partnership per limited partner unit – basic and diluted (in dollars per share)	$ 0.43	$ 0.34	$ 1.13	$ 0.92
Common Units Public
Weighted average number of limited partner units outstanding - basic and diluted (in millions):
Weighted average number of limited partner units outstanding - basic and diluted (in shares)	47.8	47.8	47.8	47.8
BP Holdco | Common Units BP Holdco
Weighted average number of limited partner units outstanding - basic and diluted (in millions):
Weighted average number of limited partner units outstanding - basic and diluted (in shares)	4.6	4.6	4.6	4.6
BP Holdco | Subordinated Units
Weighted average number of limited partner units outstanding - basic and diluted (in millions):
Weighted average number of limited partner units outstanding - basic and diluted (in shares)	52.4	52.4	52.4	52.4
Maintenance
Costs and expenses
Maintenance expenses – third parties	$ 303	$ 640	$ 1,186	$ 1,523

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Non-controlling Interests	Common UnitsPartners' CapitalGeneral Public	Common UnitsPartners' CapitalBP Holdco	Subordinated UnitsPartners' CapitalBP Holdco	General Partner
Beginning Balance at Dec. 31, 2017	$ 580,855	$ 342,330	$ 824,613	$ (47,141)	$ (538,947)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,708	10,169	13,934	1,336	15,269
Distributions to unitholders	(18,830)		(8,592)	(823)	(9,415)
Unit-based compensation	39		39
Distributions to non-controlling interests	(15,026)	(15,026)
Ending Balance at Mar. 31, 2018	585,000	337,473	828,741	(46,748)	(534,466)
Beginning Balance at Dec. 31, 2017	580,855	342,330	824,613	(47,141)	(538,947)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	124,391
Ending Balance at Sep. 30, 2018	586,793	330,040	833,006	(46,350)	(529,903)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change (Note 4)	(2,746)		(1,253)	(120)	(1,373)
Beginning Balance at Mar. 31, 2018	585,000	337,473	828,741	(46,748)	(534,466)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,192	9,722	13,902	1,333	15,235
Distributions to unitholders	(28,021)		(12,785)	(1,225)	(14,011)
Unit-based compensation	45		45
Distributions to non-controlling interests	(13,708)	(13,708)
Ending Balance at Jun. 30, 2018	583,508	333,487	829,903	(46,640)	(533,242)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,491	8,272	16,070	1,539	17,610
Distributions to unitholders	(28,543)		(13,023)	(1,249)	(14,271)
Unit-based compensation	56		56
Distributions to non-controlling interests	(11,719)	(11,719)
Ending Balance at Sep. 30, 2018	586,793	330,040	833,006	(46,350)	(529,903)
Beginning Balance at Dec. 31, 2018	210,852	140,974	836,789	(61,684)	(705,227)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,619	3,466	16,863	1,616	18,476	198
Distributions to unitholders	(31,586)		(14,413)	(1,382)	(15,791)	0
Unit-based compensation	40		40
Distributions to non-controlling interests	(4,569)	(4,569)
Ending Balance at Mar. 31, 2019	215,356	139,871	839,279	(61,450)	(702,542)	198
Beginning Balance at Dec. 31, 2018	210,852	140,974	836,789	(61,684)	(705,227)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	133,207
Ending Balance at Sep. 30, 2019	229,519	138,075	846,386	(60,781)	(694,904)	743
Beginning Balance at Mar. 31, 2019	215,356	139,871	839,279	(61,450)	(702,542)	198
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	42,195	4,864	16,851	1,615	18,462	403
Distributions to unitholders	(32,946)		(14,944)	(1,431)	(16,373)	(198)
Unit-based compensation	71		71
Distributions to non-controlling interests	(6,032)	(6,032)
Ending Balance at Jun. 30, 2019	218,644	138,703	841,257	(61,266)	(700,453)	403
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	50,393	4,639	20,540	1,968	22,503	743
Distributions to unitholders	(34,315)		(15,475)	(1,483)	(16,954)	(403)
Unit-based compensation	64		64
Distributions to non-controlling interests	(5,267)	(5,267)
Ending Balance at Sep. 30, 2019	$ 229,519	$ 138,075	$ 846,386	$ (60,781)	$ (694,904)	$ 743

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (UNAUDITED) (Parenthetical) - $ / shares	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Cash distributions per unit paid (in dollars per unit)	$ 0.3237	$ 0.3126	$ 0.3015	$ 0.2725	$ 0.2675	$ 0.1798

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net income	$ 133,207	$ 124,391
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation	1,970	1,987
Impairment and other, net	1,000	0
Non-cash expenses	212	140
Income from equity method investments	(83,312)	(66,262)
Distributions of earnings received from equity method investments	86,481	71,314
Changes in operating assets and liabilities
Accounts receivable – third parties	(166)	62
Accounts receivable – related parties	(1,074)	(380)
Prepaid expenses and other current assets	4,546	(23)
Accounts payable – third parties	(809)	494
Accounts payable – related parties	(1,071)	327
Deferred revenue and credits	1,959	729
Other current liabilities	(713)	707
Net cash provided by operating activities	142,230	133,486
Cash flows from investing activities
Capital expenditures	(375)	(1,341)
Distributions in excess of earnings from equity method investments	8,295	15,362
Net cash provided by investing activities	7,920	14,021
Cash flows from financing activities
Repayment of debt	0	(15,000)
Distributions to unitholders and general partner	(98,847)	(75,394)
Distributions to non-controlling interests	(15,868)	(40,453)
Net cash used in financing activities	(114,715)	(130,847)
Net change in cash and cash equivalents	35,435	16,660
Cash and cash equivalents at beginning of the period	56,970	32,694
Cash and cash equivalents at end of the period	92,405	49,354
Supplemental cash flow information
Cash paid for interest	12,331	581
Cash paid for lease liabilities	47	0
Non-cash investing transactions
Accrued capital expenditures	$ 346	$ 169

Business and Basis of Presentat

Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Basis of Presentation	Business and Basis of Presentation BP Midstream Partners LP (either individually or together with its subsidiaries, as the context requires, the “Partnership”) is a Delaware limited partnership formed on May 22, 2017 by BP Pipelines (North America) Inc. (“BP Pipelines”), an indirect wholly owned subsidiary of BP p.l.c. (“BP”), a “foreign private issuer” within the meaning of the Securities Exchange Act of 1934, as amended. Unless otherwise stated or the context otherwise indicates, all references to “we,” “our,” “us,” or similar expressions for time periods refer to BP Midstream Partners LP. The term “our Parent” refers to BP Pipelines; any entity that wholly owns BP Pipelines, indirectly or directly, including BP and BP America Inc. (“BPA”), an indirect wholly owned subsidiary of BP; and any entity that is wholly owned by the aforementioned entities, excluding BP Midstream Partners LP. Business We are a fee-based, growth-oriented master limited partnership formed by BP Pipelines to own, operate, develop and acquire pipelines and other midstream assets. Our assets consist of interests in entities that own crude oil, natural gas, refined products and diluent pipelines serving as key infrastructure for BP and other customers to transport onshore crude oil production to BP’s refinery in Whiting, Indiana (the “Whiting Refinery”) and offshore crude oil and natural gas production to key refining markets and trading and distribution hubs. Certain of our assets deliver refined products and diluent from the Whiting Refinery and other U.S. supply hubs to major demand centers. Acquisition of Equity Interests On October 1, 2018, pursuant to the Interest Purchase Agreement (the “Interest Purchase Agreement”) that we entered into with BP Products North America Inc. (“BP Products”), BP Offshore Pipelines Company LLC (“BP Offshore”), and BP Pipelines, we completed the acquisition of (i) an additional 45% interest in Mardi Gras Transportation System Company, LLC ("Mardi Gras"), from BP Pipelines, (ii) a 25% interest in KM Phoenix Holdings LLC, ("KM Phoenix") a Delaware limited liability company, from BP Products, and (iii) a 22.7% interest in URSA Oil Pipeline Company LLC, ("Ursa") a Delaware limited liability company, from BP Offshore, in exchange for aggregate consideration of $468 million funded with borrowings under our Credit Facility (as defined below). The purchase was accounted for as a transaction between entities under common control; as a result, we recognized the acquired assets at their historical carrying value. As of September 30, 2019, our assets consisted of the following: • BP Two Pipeline Company LLC, which owns the BP#2 crude oil pipeline system (“BP2”). • BP River Rouge Pipeline Company LLC, which owns the Whiting to River Rouge refined products pipeline system (“River Rouge”). • BP D-B Pipeline Company LLC, which owns the Diamondback diluent pipeline system (“Diamondback”). BP2, River Rouge, and Diamondback, together, are referred to as the "Wholly Owned Assets". • A 28.5% ownership interest in Mars Oil Pipeline Company, LLC (“Mars”), which owns a major corridor crude oil pipeline system in the Gulf of Mexico. • A 65% managing member interest in Mardi Gras, which holds the following investments in joint ventures located in the Gulf of Mexico: • A 56% ownership interest in Caesar Oil Pipeline Company, LLC (“Caesar”), • A 53% ownership interest in Cleopatra Gas Gathering Company, LLC (“Cleopatra”), • A 65% ownership interest in Proteus Oil Pipeline Company, LLC (“Proteus”), and, • A 65% ownership interest in Endymion Oil Pipeline Company, LLC (“Endymion”). • Together Endymion, Caesar, Cleopatra and Proteus are referred to as the “Mardi Gras Joint Ventures.” • A 25% ownership interest in KM Phoenix. • A 22.7% ownership interest in Ursa. We generate the majority of our revenue by charging fees for the transportation of crude oil, refined products and diluent through our pipelines under long-term agreements with minimum volume commitments ("MVC"). We do not engage in the marketing and trading of any commodities. All operations are conducted in the United States, and all our long-lived assets are in the United States. Our operations consist of one reportable segment. Certain businesses of ours are subject to regulation by various authorities including, but not limited to the Federal Energy Regulatory Commission ("FERC"). Regulatory bodies exercise statutory authority over matters such as common carrier tariffs, construction, rates and ratemaking and agreements with customers. Basis of Presentation Our condensed consolidated financial statements have been prepared under the rules and regulations of the Securities and Exchange Commission (“SEC”). These rules and regulations conform to the accounting principles contained in the Financial Accounting Standards Board’s (“FASB”) Accounting Standards Codification, the single source of accounting principles generally accepted in the United States (“GAAP”). Certain information and footnote disclosures normally included in the annual consolidated financial statements have been condensed or omitted from these condensed consolidated financial statements. The condensed consolidated financial statements as of September 30, 2019 , and for the three and nine months ended September 30, 2019 and 2018, included herein, are unaudited. These financial statements include all known accruals and adjustments necessary, in the opinion of management, for a fair presentation of our condensed consolidated financial position, results of operations and cash flows. Unless otherwise specified, all such adjustments are of a normal and recurring nature. The unaudited results of operations for the interim periods reported are not necessarily indicative of results to 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 Annual Report on Form 10-K for the year ended December 31, 2018 (the "2018 Annual Report"). Our financial position, results of operations and cash flows consist of consolidated BP Midstream Partners LP activities and balances. All intercompany accounts and transactions within the financial statements have been eliminated for all periods presented. Summary of Significant Accounting Policies Other than the adoption of ASU 2016-02 described below, there have been no significant changes to our accounting policies as disclosed in Note 2 - Summary of Significant Accounting Policies in our 2018 Annual Report. Standards Adopted Topic 842 On February 25, 2016, the FASB issued ASU 2016-02, “ Leases ” followed by a series of related accounting standard updates (collectively referred to as “Topic 842”). We adopted the new standard on January 1, 2019, utilizing the modified retrospective method. The new lease standard improves transparency and comparability among organizations by requiring lessees to recognize a lease liability and a corresponding right-of-use asset for virtually all lease contracts. We elected the optional transition relief under ASU 2018-11 "Leases: Targeted Improvement" which allows us to apply the transition provision at the adoption date instead of the earliest comparative period presented in our financial statements. Therefore, we recognized and measured leases existing at the adoption date but without retrospective application. See Note 3 - Leases . No cumulative effect impact was recorded to the statement of operations or beginning balance in our statement of changes in equity.

Revenue Recognition

Revenue Recognition	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition In 2018, we adopted ASU 2014-09, "Revenue from Contracts with Customers" and all related ASU’s (collectively referred to as “Topic 606”) 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. Topic 606 requires entities to recognize revenue through the application of a five-step model, which includes: (1) identification of the contract; (2) identification of the performance obligations; (3) determination of the transaction price; (4) allocation of the transaction price to the performance obligations; and (5) recognition of revenue as the entity satisfies the performance obligations. Pipeline Transportation Revenue from pipeline transportation is comprised of tariffs and fees associated with the transportation of liquid petroleum products, generally at published tariffs and in certain instances, revenue from MVC contracts at negotiated rates. Tariff revenue is recognized either at the point of delivery or at the point of receipt, pursuant to specifications outlined in the respective tariffs. Billings to BP Products for deficiency volumes under its MVCs, if any, are recorded as deferred revenue and credits, a contract liability, on our condensed consolidated balance sheets, as BP Products has the right to make up the deficiency volumes within the measurement period specified by the agreements. Deferred revenue under these arrangements is recognized into revenue once it is deemed remote that the customer will meet its required annual MVC. We recognized $2,356 of deficiency revenue under the throughput and deficiency agreements with BP Products for the three and nine months ended September 30, 2019 , and $3,857 for the three and nine months ended September 30, 2018. Allowance Oil Our tariff for crude oil transportation at BP2 includes a fixed loss allowance (“FLA”). An FLA factor per barrel, a fixed percentage, is a separate fee that is considered a part of the transaction price under the applicable crude oil tariff to cover evaporation and other losses in transit. In the three and nine months ended September 30, 2019 we recognized revenue of $2,728 and $7,824 , respectively, related to the FLA arrangements with our Parent. In the three and nine months ended September 30, 2018, we recognized revenue of $2,691 and $7,691 , respectively, related to the FLA arrangements with our Parent. Disaggregation of Revenue The following table provides information about disaggregated revenue: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Transportation services revenue - third parties $ 725 $ 508 $ 2,238 $ 2,072 Transportation services revenue - related parties 33,836 31,566 91,164 85,556 Total ASC 606 revenue $ 34,561 $ 32,074 $ 93,402 $ 87,628 Future Performance Obligations The fixed portion of our existing customer contracts are summarized in the future performance obligations as of September 30, 2019. The unfulfilled performance obligations included in the table below are expected to be recognized in revenue in the specified periods: As of September 30, 2019 Remainder of 2019 $ 29,052 2020 109,590 Total $ 138,642 Contract Balances Contract assets and contract liabilities are the result of timing differences between revenue recognition, billings and cash collections. Contract liabilities or deferred revenue and credits primarily relate to consideration received from customers for temporary deficiency quantities under minimum volume contracts that the customer has the right to make up in a future period, which we subsequently recognize as revenue or amounts we credit back to the customer in a future period. The following table provides information about receivables from contracts with customers, contract assets and contract liabilities: September 30, 2019 December 31, 2018 Receivables from contracts with customers - third parties $ 491 $ 325 Receivables from contracts with customers - related parties 10,793 9,611 Deferred revenue and credits - related parties 3,026 1,067

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	Leases We have elected the optional practical expedients permitted under the transition guidance within the new lease standard, which among other things, allows us to carry forward the historical accounting treatment relating to classification for existing leases upon adoption, allows us to not be required to reassess whether an expired or existing contract is or contains a lease, and allows us not to have to reassess initial direct costs for an existing lease. In addition, we elected the optional transition guidance related to land easements that allows us to carry forward our historical accounting treatment on existing agreements upon adoption. This allowed us to not be required to assess existing land easements that were not historically accounted for as leases under Topic 840, therefore they are excluded from this disclosure. We also elected the practical expedient to not separate lease and non-lease components for all asset classes. However, we did not elect to apply the hindsight practical expedient; therefore the non-exercised renewals were not included in the lease terms. Beginning January 1, 2019, operating right-of-use ("ROU") assets and operating lease liabilities are recognized based on the present value of lease payments over the lease term at commencement date. Because our leases do not provide an explicit rate of return, we use our incremental borrowing rate based on lease term information available at the commencement date in determining the present value of lease payments. The impact of Topic 842 on our condensed consolidated balance sheet beginning January 1, 2019 was through the recognition of ROU assets and lease liabilities for operating leases. Amounts recognized at January 1, 2019 for operating leases were as follows: January 1, 2019 ROU Assets $ 518 Current lease liability 60 Long-term lease liability 458 We have a total of four operating leases related to office space of which the term of two expires in 2036 and the other two in 2020. We have the option to terminate our leases 30 days after providing written notice of the election to terminate to the landlord. Two of our leases include a right of renewal and an annual 3% escalation on the anniversary date of lease inception. We have the option to renew our leases by giving notice to landlord not less than 60 days prior to the expiration of the lease term. We have not included the option to renew the leases in our determination of lease term because at the time of lease inception it was not certain we would exercise the renewal. We have included the variable lease payments based on the escalation percentage from above in the determination of our lease liabilities and our ROU assets. The other two leases include a non-lease component for maintenance expense. No leases include a residual value guarantee or provide us an option to acquire the real property at the end of the lease. We have no material subleasing arrangements. Amounts recognized in the accompanying condensed consolidated balance sheet are as follows: Lease activity Balance sheet location September 30, 2019 ROU assets Other assets $ 481 Current lease liability Other current liabilities 60 Long-term lease liability Other liabilities 427 As of September 30, 2019, the weighted average discount rate of our leases was 4.36% and the weighted average remaining lease term was 15.4 years . The undiscounted future minimum lease payments as of September 30, 2019 and December 31, 2018 are presented in the table below: Post-adoption ASC 842 Pre-adoption ASC 842 September 30, 2019 December 31, 2018 2019 $ 16 $ 62 2020 63 63 2021 32 32 2022 33 33 2023 34 34 Thereafter 514 514 Total $ 692 $ 738

Equity Method Investments

Equity Method Investments	9 Months Ended
	Sep. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Equity Method Investments We account for our ownership interests in Mars, Ursa, KM Phoenix and the Mardi Gras Joint Ventures using the equity method for financial reporting purposes. Our financial results include our proportionate share of the Mars, Ursa, KM Phoenix and the Mardi Gras Joint Ventures, which is reflected in Income from equity method investments on the condensed consolidated statements of operations. We did no t record any impairment loss on our equity method investments during the nine months ended September 30, 2019 and 2018. The table below summarizes the balances and activities related to each of our equity method investments ("EMI") that we recorded for the three and nine months ended September 30, 2019 and 2018: Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Percentage Ownership Distributions Received Income from EMI Carrying Value Percentage Ownership Distributions Received Income from EMI Carrying Value Mars 28.5% $ (14,250 ) $ 14,104 $ 56,874 28.5% $ (13,167 ) $ 12,241 $ 57,762 Caesar (1) 56.0% (4,760 ) 3,640 118,403 56.0% (4,760 ) 4,519 120,593 Cleopatra (1) 53.0% (2,438 ) 1,703 117,566 53.0% (2,544 ) 1,306 120,309 Proteus (1) 65.0% (4,342 ) 3,153 76,535 65.0% (3,510 ) 2,135 82,606 Endymion (1) 65.0% (3,510 ) 4,759 81,996 65.0% (3,835 ) 2,380 83,569 Others (2) Various (3,162 ) 2,745 86,201 0% — — — Total Equity Investments $ (32,462 ) $ 30,104 $ 537,575 $ (27,816 ) $ 22,581 $ 464,839 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 Percentage Ownership Distributions Received Income from EMI Carrying Value Percentage Ownership Cumulative Effect of Accounting Change (3) Distributions Received Income from EMI Carrying Value Mars 28.5% $ (40,088 ) $ 37,819 $ 56,874 28.5% $ (2,746 ) $ (36,110 ) $ 31,057 $ 57,762 Caesar (1) 56.0% (14,448 ) 13,461 118,403 56.0% — (15,357 ) 12,364 120,593 Cleopatra (1) 53.0% (9,063 ) 7,079 117,566 53.0% — (7,844 ) 4,641 120,309 Proteus (1) 65.0% (11,882 ) 7,085 76,535 65.0% — (13,585 ) 9,047 82,606 Endymion (1) 65.0% (9,945 ) 9,430 81,996 65.0% — (13,780 ) 9,153 83,569 Others (2) Various (9,350 ) 8,438 86,201 0% — — — — Total Equity Investments $ (94,776 ) $ 83,312 $ 537,575 $ (2,746 ) $ (86,676 ) $ 66,262 $ 464,839 1. These investments are held by our investment in Mardi Gras which increased to 65% from 20% on October 1, 2018. 2. Includes ownership in Ursa ( 22.7% ) and KM Phoenix ( 25% ) acquired on October 1, 2018. 3. The financial results of Mars reflected the adoption of Topic 606 on January 1, 2018 under the modified retrospective transition method through a cumulative adjustment to equity. Our cumulative effect impact from this accounting change to our Mars investment was $(2,746) , offset to equity. The Mardi Gras Joint Ventures and Ursa adopted this ASU on January 1, 2019 and there was no cumulative effect impact from the adoption. KM Phoenix adopted Topic 606 on January 1, 2018 and there was no cumulative effect impact from the adoption. The following table presents aggregated selected income statement data for our equity method investments on a 100% basis for the three and nine months ended September 30, 2019 and 2018: Three Months Ended September 30, 2019 2018 (1) Statement of operations Revenue $ 146,090 $ 124,644 Operating expenses 63,313 53,994 Net income 83,039 70,761 Nine Months Ended September 30, 2019 2018 (1) Statement of operations Revenue $ 410,232 $ 339,931 Operating expenses 180,277 147,024 Net income 231,413 193,248 1. Balances include KM Phoenix and Ursa results.

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment consisted of the following: September 30, 2019 December 31, 2018 Land $ 155 $ 155 Right-of-way assets 1,380 1,380 Buildings and improvements 9,332 12,032 Pipelines and equipment 93,951 93,617 Other 514 509 Construction in progress 463 277 Property, plant and equipment 105,795 107,970 Less: Accumulated depreciation (40,929 ) (39,390 ) Property, plant and equipment, net $ 64,866 $ 68,580 During the nine months ended September 30, 2019, an impairment charge of $2.3 million was recorded under "Impairment and other, net" on our condensed consolidated statements of operations. See Note 12 - Commitments and Contingencies . There were no impairments during the period ended December 31, 2018.

Other Current Liabilities

Other Current Liabilities	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Other Current Liabilities	Other Current Liabilities Other current liabilities consisted of the following: September 30, 2019 December 31, 2018 Current portion of environmental remediation obligations $ 620 $ 629 Current portion of lease liabilities 60 — Accrued interest payable - related parties 4,155 4,155 Accrued liabilities 1,912 2,116 Other current liabilities $ 6,747 $ 6,900

Debt

Debt	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt	Debt On October 30, 2017, the Partnership entered into a $600 million unsecured revolving credit facility agreement (the “Credit Facility”) with an affiliate of BP. A summary of certain key terms and covenants of the Credit Facility is included in our financial statements included in our 2018 Annual Report in Note 8 - Debt . As of September 30, 2019 , the Partnership was in compliance with the covenants contained in the Credit Facility. On October 1, 2018, the Partnership borrowed $468 million under the Credit Facility to fund our acquisition. See Note 1 - Business and Basis of Presentation. On February 20, 2019, we entered into a Credit Facility Waiver Agreement (“First Waiver Agreement”) whereby the lender waived certain terms on our outstanding $468 million borrowings. The original loan repayment date of March 29, 2019 was waived and amended and modified to April 1, 2020. On May 3, 2019, we entered into a Second Credit Facility Waiver Agreement (“Second Waiver Agreement”) whereby the lender waived certain terms on our outstanding $468 million borrowings. The amended loan repayment date of April 1, 2020 was waived and amended and modified to November 30, 2020. Accrued interest will be paid on the 25th day of April, July, October and January of each year. Any remaining interest will be paid on November 30, 2020. All other terms of the Credit Facility remain the same. Pursuant to the First Waiver Agreement and Second Waiver Agreement, we classified the $468 million outstanding as long-term debt on our condensed consolidated balance sheet at September 30, 2019 and December 31, 2018 . There were $468 million of outstanding borrowings under the Credit Facility at September 30, 2019 and December 31, 2018 . Interest charges and fees related to the Credit Facility were $4.1 million and $12.3 million for the three and nine months ended September 30, 2019 , respectively, and $0.2 million and $0.6 million for the three and nine months ended September 30, 2018 , respectively. For the three and nine months ended September 30, 2019 , the weighted average interest rate for the Credit Facility was 3.25% . For the three and nine months ended September 30, 2018 , the weighted average interest rate for the Credit Facility was 2.24% . This facility includes customary fees, including a commitment fee of 0.10% and a utilization fee of 0.20% per annum.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Related party transactions include transactions with our Parent and our Parent’s affiliates, including those entities in which our Parent has an ownership interest but does not have control. In addition to the FLA arrangements discussed in Note 2- Revenue Recognition and the Credit Facility discussed above, we have entered into the following transactions with our related parties: Omnibus Agreement The Partnership has entered into an omnibus agreement with BP Pipelines and certain of its affiliates, including BP Midstream Partners GP LLC (our "General Partner"). This agreement addresses, among other things, (i) the Partnership's obligation to pay an annual fee for general and administrative services provided by BP Pipelines and its affiliates, (ii) the Partnership's obligation to reimburse BP Pipelines for personnel and other costs related to the direct operation, management and maintenance of the assets and (iii) the Partnership's obligation to reimburse BP Pipelines for services and certain direct or allocated costs and expenses incurred by BP Pipelines or its affiliates on behalf of the Partnership. BP Pipelines will indemnify us for all known and certain unknown environmental liabilities that are associated with the ownership or operation of our assets and due to occurrences on or before October 30, 2017, subject to certain limitations. Indemnification for any unknown environmental liabilities will be limited to liabilities due to occurrences on or before October 30, 2017, which are identified prior to October 30, 2020. Further, the omnibus agreement addresses the granting of a license from BPA to the Partnership with respect to use of certain BP trademarks and trade name. Cash Management Program We have established our own cash accounts for the funding of our operating and investing activities but continue to participate in our Parent’s centralized cash management and funding system. Related Party Revenue We provide crude oil, refined products and diluent transportation services to related parties and generate revenue through published tariffs. We have commercial arrangements with BP Products that include MVC. See Note 9 - Related Party Transactions in our financial statements included in our 2018 Annual Report for further discussion regarding these agreements. Our revenue from related parties was $33,836 and $91,164 for the three and nine months ended September 30, 2019 , respectively, and $31,566 and $85,556 for the three and nine months ended September 30, 2018 , respectively. We recognized $2,356 of deficiency revenue under the throughput and deficiency agreements with BP Products for the three and nine months ended September 30, 2019 , and $3,857 for the three and nine months ended September 30, 2018. We recorded $3,026 and $1,067 in Deferred revenue and credits on our condensed consolidated balance sheets at September 30, 2019 and December 31, 2018 , respectively. Related Party Expenses All employees performing services on behalf of our operations are employees of our Parent. Our Parent also procures our insurance policies on our behalf and performs certain general corporate functions for us related to finance, accounting, treasury, legal, information technology, human resources, shared services, government affairs, insurance, health, safety, security, employee benefits, incentives, severance and environmental functional support. Personnel and operating costs incurred by our Parent on our behalf are included in either Operating expenses – related parties or General and administrative – related parties in the condensed consolidated statements of operations, depending on the nature of the service provided. We paid our Parent an annual fee of $13.3 million in 2018 in the form of monthly installments under the omnibus agreement for general and administrative services provided by our Parent and its affiliates. The annual fee was adjusted to $13.6 million per year, payable in equal monthly installments, beginning on January 1, 2019. We also reimburse our Parent for personnel and other costs related to the direct operation, management and maintenance of the assets and services and certain direct or allocated costs and expenses incurred by our Parent or its affiliates on our behalf pursuant to the terms in the omnibus agreement. For the three and nine months ended September 30, 2019 and 2018, we recorded the following amounts for related party expenses, which also included the expenses related to share-based compensation discussed below: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Operating expenses—related parties $ 1,423 $ 1,506 $ 4,317 $ 3,494 Maintenance expenses—related parties 66 31 139 75 General and administrative—related parties 3,476 3,691 10,597 10,556 Total costs and expenses—related parties $ 4,965 $ 5,228 $ 15,053 $ 14,125 Share-based Compensation Our Parent operates share option plans and equity-settled employee share plans. These plans typically have a three -year performance or restricted period during which the units accrue net notional dividends, which are treated as having been reinvested. Leaving employment will normally preclude the conversion of units into shares, but special arrangements apply for participants that leave for qualifying reasons. Share-based compensation related to the employees of our Parent who provide services to us is charged to the Partnership pursuant to the terms of the omnibus agreement. The Partnership also issued its own unit-based compensation under our long-term incentive plan. See Note 13 - Unit-Based Compensation. Non-controlling Interests Non-controlling interests consist of the 80% ownership interest in Mardi Gras held by our Parent at September 30, 2018 compared to the 35% ownership interest held at September 30, 2019 after completion of the acquisition on October 1, 2018. Net income attributable to non-controlling interests is the product of the non-controlling interests ownership percentage and the net income of Mardi Gras. We report Non-controlling interests as a separate component of equity on our condensed consolidated balance sheets and Net income attributable to non-controlling interests on our condensed consolidated statements of operations.

Net Income Per Limited Partner

Net Income Per Limited Partner Unit	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Income Per Limited Partner Unit	Net Income Per Limited Partner Unit The following table details the distributions declared and/or paid for the periods presented: Three Months Ended Date Paid or General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions per Limited Partner Unit March 31, 2018 May 15, 2018 $ — $ 14,010 $ 14,011 $ 28,021 $ 0.2675 June 30, 2018 August 15, 2018 — 14,272 14,271 28,543 0.2725 September 30, 2018 November 15, 2018 — 15,268 15,268 30,536 0.2915 March 31, 2019 May 15, 2019 198 16,375 16,373 32,946 0.3126 June 30, 2019 August 14, 2019 403 16,958 16,954 34,315 0.3237 September 30, 2019 November 14, 2019 743 17,576 17,572 35,891 0.3355 Earnings in excess of distributions are allocated to the limited partners based on their respective percentage interests. Payments made to the Partnership’s unitholders are determined in relation to actual distributions declared and are not based on the net income allocations used in the calculation of net income per unit. In addition to the common and subordinated units, the Partnership also identified the incentive distribution rights ("IDRs") currently held by the General Partner as a participating security and uses the two-class method when calculating the net income per unit applicable to limited partners that is based on the weighted-average number of common units outstanding during the period. When calculating basic earnings per unit under the two-class method for a master limited partnership, net income for the current reporting period is reduced by the amount of available cash that will be distributed to the General Partner and limited partners for that reporting period. The following tables show the allocation of net income to arrive at net income per limited partner unit for the three and nine months ended September 30, 2019 and 2018: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Net income attributable to the Partnership $ 45,754 $ 35,219 $ 120,238 $ 96,228 Less: Incentive distribution rights currently held by the General Partner 743 — 1,344 — Limited partners' distribution declared on common units 17,576 15,268 50,909 43,550 Limited partners' distribution declared on subordinated units 17,572 15,268 50,899 43,550 Net income attributable to the Partnership in excess of distributions $ 9,863 $ 4,683 $ 17,086 $ 9,128 Three Months Ended September 30, 2019 General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions declared $ 743 $ 17,576 $ 17,572 $ 35,891 Net income attributable to the Partnership in excess of distributions — 4,932 4,931 9,863 Net income attributable to the Partnership $ 743 $ 22,508 $ 22,503 $ 45,754 Weighted average units outstanding (in millions): Basic and Diluted 52.4 52.4 104.8 Net income per limited partner unit (in dollars): Basic and Diluted $ 0.43 $ 0.43 Nine Months Ended September 30, 2019 General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions declared $ 1,344 $ 50,909 $ 50,899 $ 103,152 Net income attributable to the Partnership in excess of distributions — 8,544 8,542 17,086 Net income attributable to the Partnership $ 1,344 $ 59,453 $ 59,441 $ 120,238 Weighted average units outstanding (in millions): Basic and Diluted 52.4 52.4 104.8 Net income per limited partner unit (in dollars): Basic and Diluted $ 1.13 $ 1.13 Three Months Ended September 30, 2018 General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions declared $ — $ 15,268 $ 15,268 $ 30,536 Net income attributable to the Partnership in excess of distributions — 2,341 2,342 4,683 Net income attributable to the Partnership $ — $ 17,609 $ 17,610 $ 35,219 Weighted average units outstanding (in millions): Basic and Diluted 52.4 52.4 104.8 Net income per limited partner unit (in dollars): Basic and Diluted $ 0.34 $ 0.34 Nine Months Ended September 30, 2018 General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions declared $ — $ 43,550 $ 43,550 $ 87,100 Net income attributable to the Partnership in excess of distributions — 4,564 4,564 9,128 Net income attributable to the Partnership $ — $ 48,114 $ 48,114 $ 96,228 Weighted average units outstanding (in millions): Basic and Diluted 52.4 52.4 104.8 Net income per limited partner unit (in dollars): Basic and Diluted $ 0.92 $ 0.92

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. We classify the fair value of an asset or liability based on the lowest level of input significant to its measurement. A fair value initially reported as Level 3 will be subsequently reported as Level 2 if the unobservable inputs become inconsequential to its measurement, or corroborating market data becomes available. Asset and liability fair values initially reported as Level 2 will be subsequently reported as Level 3 if corroborating market data becomes unavailable. The carrying amounts of our accounts receivable, other current assets, accounts payable, deferred revenue and credits, and other current liabilities approximate their fair values due to their short-term nature.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes BP Midstream Partners LP is not a taxable entity for U.S. federal and state income tax purposes. Taxes on our net income are generally borne by our partners through the allocation of taxable income. The condensed consolidated financial statements, therefore, do not include a provision for income tax.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings We are party to ongoing legal proceedings in the ordinary course of business. For each of our outstanding legal matters, if any, 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 the outcome of these proceedings cannot be predicted with certainty, we do not believe the results of these proceedings, individually or in the aggregate, will have a material adverse effect on our business, financial condition, results of operations or liquidity. Indemnification Under our omnibus agreement, our Parent will indemnify us for certain environmental liabilities, litigation and other matters attributable to the ownership or operation of our assets prior to our ownership. For the purposes of determining the indemnified amount of any loss suffered or incurred by the Partnership, the Partnership’s ownership of 28.5% in Mars, and 65% in Mardi Gras, and Mardi Gras’ 56% ownership in Caesar, 53% ownership in Cleopatra, 65% ownership in Endymion and 65% ownership in Proteus will be considered. Indemnification for certain identified environmental liabilities is subject to a cap of $25.0 million without any deductible. Other matters covered by the omnibus agreement are subject to a cap of $15.0 million and an aggregate deductible of $0.5 million before we are entitled to indemnification. Indemnification for any unknown environmental liabilities is limited to liabilities due to occurrences prior to the closing of the IPO and that are identified before the third anniversary of the closing of the IPO. The Interest Purchase Agreement contains customary representations, warranties and covenants of our Parent and the Partnership. Our Parent, on the one hand, and the Partnership, on the other hand, have agreed to indemnify each other and their respective affiliates, officers, directors and other representatives against certain losses, including those resulting from any breach of their representations, warranties or covenants contained in the Interest Purchase Agreement, subject to certain limitations and survival periods. This agreement covers the Partnership’s ownership of 22.7% in Ursa and 25% in KM Phoenix. Environmental Matters We are subject to federal, state, and local environmental laws and regulations. We record provisions for environmental liabilities based on management’s best estimates, using all information that is available at the time. 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 progress, additional information is obtained, requiring revisions to estimated costs. We are indemnified by our Parent under the omnibus agreement against environmental cleanup costs for incidents that occurred prior to our ownership. Revisions to the estimated environmental liability for conditions that are not indemnified under the omnibus agreement with our Parent are reflected in our condensed consolidated statements of operations in the year in which they are probable and reasonably estimable. We accrued $3,760 and $3,853 for environmental liabilities at September 30, 2019 and December 31, 2018 , respectively. These balances are broken down on the condensed consolidated balance sheets as follows: Balance sheet location September 30, 2019 December 31, 2018 Current portion of environmental remediation obligations Other current liabilities $ 620 $ 629 Long-term portion of environmental remediation obligations Other liabilities 3,140 3,224 Total $ 3,760 $ 3,853 The balances are related to incidents that occurred prior to our ownership and are entirely indemnified by our Parent. As a result, we recorded $3,760 and $3,853 for corresponding indemnification assets at September 30, 2019 and December 31, 2018 , respectively. These balances are broken down on the condensed consolidated balance sheets as follows: Balance sheet location September 30, 2019 December 31, 2018 Current portion of indemnification assets Other current assets $ 620 $ 629 Non-current portion of indemnification assets Other assets 3,140 3,224 Total $ 3,760 $ 3,853 Griffith Station Incident On June 13, 2019, a building fire occurred at the Griffith Station on BP2. Management has performed an initial evaluation of the assets and determined that an impairment is required. A charge of $2.3 million for the impairment was recorded under "Impairment and other, net" on our condensed consolidated statements of operations for the three months ended June 30, 2019. In addition, we incurred $0.8 million for response expense during the three months ended June 30, 2019 and $0.5 million during the three months ended September 30, 2019. Our assets are insured with a deductible of $1.0 million per incident. We have accrued an offsetting insurance receivable of $2.6 million

Unit-Based Compensation

Unit-Based Compensation	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Unit-Based Compensation	Unit-Based Compensation Long-Term Incentive Plan Our General Partner has adopted the BP Midstream Partners LP 2017 Long Term Incentive Plan (the “LTIP”). Awards under the LTIP are available for eligible officers, directors, employees and consultants of the General Partner and its affiliates, who perform services for the Partnership. The LTIP allows the Partnership to grant unit options, unit appreciation rights, restricted units, phantom units, unit awards, cash awards, performance awards, distribution equivalent rights, substitute awards and other unit-based awards. The maximum aggregate number of common units that may be issued pursuant to the awards granted under the LTIP shall not exceed 5,502,271 , subject to proportionate adjustment in the event of unit splits and similar events. Unit-Based Awards under the LTIP The following is a summary of phantom unit award activities of the Partnership’s common units for the nine months ended September 30, 2019 : Phantom Units Number of Units (in units) Weighted Average Grant Date Fair Value per Unit (in dollars) Outstanding at December 31, 2018 3,737 $ 20.07 Granted 15,227 16.64 Vested (3,737 ) 20.07 Outstanding at September 30, 2019 15,227 $ 16.64 For the three and nine months ended September 30, 2019 , total compensation expense recognized for phantom unit awards was approximately $64 and $175 , respectively. For the three and nine months ended September 30, 2018, total compensation expense recognized for phantom unit awards was approximately $56 and $140 , respectively. The unrecognized compensation cost related to phantom unit awards was approximately $105 at September 30, 2019 , which is expected to be recognized over a weighted average period of 0.4 years

Variable Interest Entity

Variable Interest Entity	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entity	Variable Interest Entity Mardi Gras is a Delaware corporation and a pass-through entity for federal and state income tax purposes. Mardi Gras holds equity interests in the Mardi Gras Joint Ventures and accounts for them as equity method investments. Mardi Gras does not have any other operations or activities. The remaining interests in each of the Mardi Gras Joint Ventures are owned by unaffiliated third-party investors. Each of the Mardi Gras Joint Ventures is managed by their respective management committee, and decisions made by these management committees require approval of two or more members that are not affiliates with equity interest holdings meeting certain thresholds. On October 30, 2017, our Parent contributed to us 20% of its economic interest and 100% of its managing member interest in Mardi Gras. The remainder of the economic interest in Mardi Gras was held 79% by BP Pipelines and 1% by an affiliate of BP. Through our managing member interest in Mardi Gras, we have the right to vote 100% of Mardi Gras’ interest in each of the Mardi Gras Joint Ventures. We determined that Mardi Gras is a variable interest entity because (i) we hold disproportional voting rights as compared to our economic interest in Mardi Gras, and (ii) substantially all of Mardi Gras’ activities involve or are conducted on behalf of our Parent, which holds disproportionately few voting rights. On October 1, 2018, pursuant to the Interest Purchase Agreement we completed the acquisition of an additional 45% interest in Mardi Gras from BP Pipelines. This reduced the non-controlling interest on Mardi Gras from 80% to 35% . The managing member interest in Mardi Gras provides us with the unilateral power to direct the activities of Mardi Gras that most significantly impact its economic performance including the right to exercise the voting rights of BP for each of the Mardi Gras Joint Ventures. In addition, our obligations to absorb the expected losses of and the right to receive the residual returns from Mardi Gras relative to our economic ownership is significant to Mardi Gras. As a result, we are the primary beneficiary of Mardi Gras and consolidate Mardi Gras. We have the obligation to provide financial support to Mardi Gras if all members unanimously determine that additional capital contributions are necessary to fund Mardi Gras’ operations. The assets of Mardi Gras can only be used to satisfy its own obligations, which were zero at September 30, 2019 and December 31, 2018. Under the current limited liability company agreement of Mardi Gras, creditors of Mardi Gras, if any, do not have any recourse to the general credit of the Partnership. The financial position of Mardi Gras at September 30, 2019 and December 31, 2018 , its financial performance for the three and six months ended September 30, 2019 and 2018 and cash flows for the nine months ended September 30, 2019 and 2018, as reflected in our condensed consolidated financial statements, are as follows: September 30, 2019 December 31, 2018 Balance sheet Equity method investments $ 394,500 $ 402,783 Non-controlling interests 138,075 140,974 Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Statement of operations Income from equity method investments $ 13,255 $ 10,340 $ 37,055 $ 35,205 Less: Net income attributable to non-controlling interests 4,639 8,272 12,969 28,163 Net impact on Net income attributable to the Partnership $ 8,616 $ 2,068 $ 24,086 $ 7,042 Nine Months Ended September 30, 2019 2018 Statement of cash flows Cash flows from operating activities Distributions of earnings received from equity method investments $ 37,055 $ 35,205 Cash flows from investing activities Distribution in excess of earnings from equity method investments 8,283 15,362 Cash flows from financing activities Distributions to non-controlling interests (15,868 ) (40,453 ) Net change on the Partnership's cash and cash equivalents $ 29,470 $ 10,114

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events We have evaluated subsequent events through the issuance of these condensed consolidated financial statements. Based on this evaluation, it was determined that no subsequent events occurred, other than the distribution noted below, that require recognition or disclosure in the condensed consolidated financial statements. Distribution On October 17, 2019, we declared a cash distribution of $0.3355 per limited partner unit to unitholders of record on October 31, 2019, for the three months ended September 30, 2019. The distribution, combined with distributions to our General Partner, will be paid on November 14, 2019 and will total $35.9 million , with $16.0 million being distributed to our non-affiliated common unitholders and $19.9 million , including $0.7 million for IDRs, being distributed to our Parent in respect of its ownership of our common units, subordinated units and IDRs.

Business and Basis of Present_2

Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Our condensed consolidated financial statements have been prepared under the rules and regulations of the Securities and Exchange Commission (“SEC”). These rules and regulations conform to the accounting principles contained in the Financial Accounting Standards Board’s (“FASB”) Accounting Standards Codification, the single source of accounting principles generally accepted in the United States (“GAAP”). Certain information and footnote disclosures normally included in the annual consolidated financial statements have been condensed or omitted from these condensed consolidated financial statements. The condensed consolidated financial statements as of September 30, 2019 , and for the three and nine months ended September 30, 2019 and 2018, included herein, are unaudited. These financial statements include all known accruals and adjustments necessary, in the opinion of management, for a fair presentation of our condensed consolidated financial position, results of operations and cash flows. Unless otherwise specified, all such adjustments are of a normal and recurring nature. The unaudited results of operations for the interim periods reported are not necessarily indicative of results to 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 Annual Report on Form 10-K for the year ended December 31, 2018 (the "2018 Annual Report"). Our financial position, results of operations and cash flows consist of consolidated BP Midstream Partners LP activities and balances. All intercompany accounts and transactions within the financial statements have been eliminated for all periods presented.
Standards Adopted	Standards Adopted Topic 842 On February 25, 2016, the FASB issued ASU 2016-02, “ Leases ” followed by a series of related accounting standard updates (collectively referred to as “Topic 842”). We adopted the new standard on January 1, 2019, utilizing the modified retrospective method. The new lease standard improves transparency and comparability among organizations by requiring lessees to recognize a lease liability and a corresponding right-of-use asset for virtually all lease contracts. We elected the optional transition relief under ASU 2018-11 "Leases: Targeted Improvement" which allows us to apply the transition provision at the adoption date instead of the earliest comparative period presented in our financial statements. Therefore, we recognized and measured leases existing at the adoption date but without retrospective application. See Note 3 - Leases . No cumulative effect impact was recorded to the statement of operations or beginning balance in our statement of changes in equity.
Revenue Recognition	Revenue Recognition In 2018, we adopted ASU 2014-09, "Revenue from Contracts with Customers" and all related ASU’s (collectively referred to as “Topic 606”) 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. Topic 606 requires entities to recognize revenue through the application of a five-step model, which includes: (1) identification of the contract; (2) identification of the performance obligations; (3) determination of the transaction price; (4) allocation of the transaction price to the performance obligations; and (5) recognition of revenue as the entity satisfies the performance obligations. Pipeline Transportation Revenue from pipeline transportation is comprised of tariffs and fees associated with the transportation of liquid petroleum products, generally at published tariffs and in certain instances, revenue from MVC contracts at negotiated rates. Tariff revenue is recognized either at the point of delivery or at the point of receipt, pursuant to specifications outlined in the respective tariffs. Billings to BP Products for deficiency volumes under its MVCs, if any, are recorded as deferred revenue and credits, a contract liability, on our condensed consolidated balance sheets, as BP Products has the right to make up the deficiency volumes within the measurement period specified by the agreements. Deferred revenue under these arrangements is recognized into revenue once it is deemed remote that the customer will meet its required annual MVC. We recognized $2,356 of deficiency revenue under the throughput and deficiency agreements with BP Products for the three and nine months ended September 30, 2019 , and $3,857 for the three and nine months ended September 30, 2018. Allowance Oil Our tariff for crude oil transportation at BP2 includes a fixed loss allowance (“FLA”). An FLA factor per barrel, a fixed percentage, is a separate fee that is considered a part of the transaction price under the applicable crude oil tariff to cover evaporation and other losses in transit.

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table provides information about disaggregated revenue: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Transportation services revenue - third parties $ 725 $ 508 $ 2,238 $ 2,072 Transportation services revenue - related parties 33,836 31,566 91,164 85,556 Total ASC 606 revenue $ 34,561 $ 32,074 $ 93,402 $ 87,628
Summary of Remaining Performance Obligation, Expected Timing of Satisfaction	The fixed portion of our existing customer contracts are summarized in the future performance obligations as of September 30, 2019. The unfulfilled performance obligations included in the table below are expected to be recognized in revenue in the specified periods: As of September 30, 2019 Remainder of 2019 $ 29,052 2020 109,590 Total $ 138,642
Summary of Contract with Customer, Assets and Liabilities	The following table provides information about receivables from contracts with customers, contract assets and contract liabilities: September 30, 2019 December 31, 2018 Receivables from contracts with customers - third parties $ 491 $ 325 Receivables from contracts with customers - related parties 10,793 9,611 Deferred revenue and credits - related parties 3,026 1,067

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Summary of Balance Sheet Impact and Balances	Amounts recognized in the accompanying condensed consolidated balance sheet are as follows: Lease activity Balance sheet location September 30, 2019 ROU assets Other assets $ 481 Current lease liability Other current liabilities 60 Long-term lease liability Other liabilities 427 January 1, 2019 ROU Assets $ 518 Current lease liability 60 Long-term lease liability 458
Schedule of Future Minimum Lease Payments Under 842	The undiscounted future minimum lease payments as of September 30, 2019 and December 31, 2018 are presented in the table below: Post-adoption ASC 842 Pre-adoption ASC 842 September 30, 2019 December 31, 2018 2019 $ 16 $ 62 2020 63 63 2021 32 32 2022 33 33 2023 34 34 Thereafter 514 514 Total $ 692 $ 738
Schedule of Future Minimum Rental Payments for Operating Leases Under Topic 840	The undiscounted future minimum lease payments as of September 30, 2019 and December 31, 2018 are presented in the table below: Post-adoption ASC 842 Pre-adoption ASC 842 September 30, 2019 December 31, 2018 2019 $ 16 $ 62 2020 63 63 2021 32 32 2022 33 33 2023 34 34 Thereafter 514 514 Total $ 692 $ 738

Equity Method Investments (Tabl

Equity Method Investments (Tables)	9 Months Ended
	Sep. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Equity Method Investments	The table below summarizes the balances and activities related to each of our equity method investments ("EMI") that we recorded for the three and nine months ended September 30, 2019 and 2018: Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Percentage Ownership Distributions Received Income from EMI Carrying Value Percentage Ownership Distributions Received Income from EMI Carrying Value Mars 28.5% $ (14,250 ) $ 14,104 $ 56,874 28.5% $ (13,167 ) $ 12,241 $ 57,762 Caesar (1) 56.0% (4,760 ) 3,640 118,403 56.0% (4,760 ) 4,519 120,593 Cleopatra (1) 53.0% (2,438 ) 1,703 117,566 53.0% (2,544 ) 1,306 120,309 Proteus (1) 65.0% (4,342 ) 3,153 76,535 65.0% (3,510 ) 2,135 82,606 Endymion (1) 65.0% (3,510 ) 4,759 81,996 65.0% (3,835 ) 2,380 83,569 Others (2) Various (3,162 ) 2,745 86,201 0% — — — Total Equity Investments $ (32,462 ) $ 30,104 $ 537,575 $ (27,816 ) $ 22,581 $ 464,839 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 Percentage Ownership Distributions Received Income from EMI Carrying Value Percentage Ownership Cumulative Effect of Accounting Change (3) Distributions Received Income from EMI Carrying Value Mars 28.5% $ (40,088 ) $ 37,819 $ 56,874 28.5% $ (2,746 ) $ (36,110 ) $ 31,057 $ 57,762 Caesar (1) 56.0% (14,448 ) 13,461 118,403 56.0% — (15,357 ) 12,364 120,593 Cleopatra (1) 53.0% (9,063 ) 7,079 117,566 53.0% — (7,844 ) 4,641 120,309 Proteus (1) 65.0% (11,882 ) 7,085 76,535 65.0% — (13,585 ) 9,047 82,606 Endymion (1) 65.0% (9,945 ) 9,430 81,996 65.0% — (13,780 ) 9,153 83,569 Others (2) Various (9,350 ) 8,438 86,201 0% — — — — Total Equity Investments $ (94,776 ) $ 83,312 $ 537,575 $ (2,746 ) $ (86,676 ) $ 66,262 $ 464,839 1. These investments are held by our investment in Mardi Gras which increased to 65% from 20% on October 1, 2018. 2. Includes ownership in Ursa ( 22.7% ) and KM Phoenix ( 25% ) acquired on October 1, 2018. 3. The financial results of Mars reflected the adoption of Topic 606 on January 1, 2018 under the modified retrospective transition method through a cumulative adjustment to equity. Our cumulative effect impact from this accounting change to our Mars investment was $(2,746) , offset to equity. The Mardi Gras Joint Ventures and Ursa adopted this ASU on January 1, 2019 and there was no cumulative effect impact from the adoption. KM Phoenix adopted Topic 606 on January 1, 2018 and there was no cumulative effect impact from the adoption. The following table presents aggregated selected income statement data for our equity method investments on a 100% basis for the three and nine months ended September 30, 2019 and 2018: Three Months Ended September 30, 2019 2018 (1) Statement of operations Revenue $ 146,090 $ 124,644 Operating expenses 63,313 53,994 Net income 83,039 70,761 Nine Months Ended September 30, 2019 2018 (1) Statement of operations Revenue $ 410,232 $ 339,931 Operating expenses 180,277 147,024 Net income 231,413 193,248 1. Balances include KM Phoenix and Ursa results.

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Components of Property, Plant and Equipment	Property, plant and equipment consisted of the following: September 30, 2019 December 31, 2018 Land $ 155 $ 155 Right-of-way assets 1,380 1,380 Buildings and improvements 9,332 12,032 Pipelines and equipment 93,951 93,617 Other 514 509 Construction in progress 463 277 Property, plant and equipment 105,795 107,970 Less: Accumulated depreciation (40,929 ) (39,390 ) Property, plant and equipment, net $ 64,866 $ 68,580

Other Current Liabilities (Tabl

Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Schedule of Other Current Liabilities	Other current liabilities consisted of the following: September 30, 2019 December 31, 2018 Current portion of environmental remediation obligations $ 620 $ 629 Current portion of lease liabilities 60 — Accrued interest payable - related parties 4,155 4,155 Accrued liabilities 1,912 2,116 Other current liabilities $ 6,747 $ 6,900

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	For the three and nine months ended September 30, 2019 and 2018, we recorded the following amounts for related party expenses, which also included the expenses related to share-based compensation discussed below: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Operating expenses—related parties $ 1,423 $ 1,506 $ 4,317 $ 3,494 Maintenance expenses—related parties 66 31 139 75 General and administrative—related parties 3,476 3,691 10,597 10,556 Total costs and expenses—related parties $ 4,965 $ 5,228 $ 15,053 $ 14,125

Net Income Per Limited Partne_2

Net Income Per Limited Partner Unit (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Distributions	The following table details the distributions declared and/or paid for the periods presented: Three Months Ended Date Paid or General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions per Limited Partner Unit March 31, 2018 May 15, 2018 $ — $ 14,010 $ 14,011 $ 28,021 $ 0.2675 June 30, 2018 August 15, 2018 — 14,272 14,271 28,543 0.2725 September 30, 2018 November 15, 2018 — 15,268 15,268 30,536 0.2915 March 31, 2019 May 15, 2019 198 16,375 16,373 32,946 0.3126 June 30, 2019 August 14, 2019 403 16,958 16,954 34,315 0.3237 September 30, 2019 November 14, 2019 743 17,576 17,572 35,891 0.3355
Schedule of Earnings Per Share	The following tables show the allocation of net income to arrive at net income per limited partner unit for the three and nine months ended September 30, 2019 and 2018: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Net income attributable to the Partnership $ 45,754 $ 35,219 $ 120,238 $ 96,228 Less: Incentive distribution rights currently held by the General Partner 743 — 1,344 — Limited partners' distribution declared on common units 17,576 15,268 50,909 43,550 Limited partners' distribution declared on subordinated units 17,572 15,268 50,899 43,550 Net income attributable to the Partnership in excess of distributions $ 9,863 $ 4,683 $ 17,086 $ 9,128 Three Months Ended September 30, 2019 General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions declared $ 743 $ 17,576 $ 17,572 $ 35,891 Net income attributable to the Partnership in excess of distributions — 4,932 4,931 9,863 Net income attributable to the Partnership $ 743 $ 22,508 $ 22,503 $ 45,754 Weighted average units outstanding (in millions): Basic and Diluted 52.4 52.4 104.8 Net income per limited partner unit (in dollars): Basic and Diluted $ 0.43 $ 0.43 Nine Months Ended September 30, 2019 General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions declared $ 1,344 $ 50,909 $ 50,899 $ 103,152 Net income attributable to the Partnership in excess of distributions — 8,544 8,542 17,086 Net income attributable to the Partnership $ 1,344 $ 59,453 $ 59,441 $ 120,238 Weighted average units outstanding (in millions): Basic and Diluted 52.4 52.4 104.8 Net income per limited partner unit (in dollars): Basic and Diluted $ 1.13 $ 1.13 Three Months Ended September 30, 2018 General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions declared $ — $ 15,268 $ 15,268 $ 30,536 Net income attributable to the Partnership in excess of distributions — 2,341 2,342 4,683 Net income attributable to the Partnership $ — $ 17,609 $ 17,610 $ 35,219 Weighted average units outstanding (in millions): Basic and Diluted 52.4 52.4 104.8 Net income per limited partner unit (in dollars): Basic and Diluted $ 0.34 $ 0.34 Nine Months Ended September 30, 2018 General Partner Limited Partners' Common Units Limited Partners' Subordinated Units Total Distributions declared $ — $ 43,550 $ 43,550 $ 87,100 Net income attributable to the Partnership in excess of distributions — 4,564 4,564 9,128 Net income attributable to the Partnership $ — $ 48,114 $ 48,114 $ 96,228 Weighted average units outstanding (in millions): Basic and Diluted 52.4 52.4 104.8 Net income per limited partner unit (in dollars): Basic and Diluted $ 0.92 $ 0.92

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Summary of Balance Sheet Classification of Environmental Liabilities	These balances are broken down on the condensed consolidated balance sheets as follows: Balance sheet location September 30, 2019 December 31, 2018 Current portion of environmental remediation obligations Other current liabilities $ 620 $ 629 Long-term portion of environmental remediation obligations Other liabilities 3,140 3,224 Total $ 3,760 $ 3,853
Schedule Of Indemnification Asset For Environmental Loss Contingencies	These balances are broken down on the condensed consolidated balance sheets as follows: Balance sheet location September 30, 2019 December 31, 2018 Current portion of indemnification assets Other current assets $ 620 $ 629 Non-current portion of indemnification assets Other assets 3,140 3,224 Total $ 3,760 $ 3,853

Unit-Based Compensation (Tables

Unit-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Phantom Units Activity	The following is a summary of phantom unit award activities of the Partnership’s common units for the nine months ended September 30, 2019 : Phantom Units Number of Units (in units) Weighted Average Grant Date Fair Value per Unit (in dollars) Outstanding at December 31, 2018 3,737 $ 20.07 Granted 15,227 16.64 Vested (3,737 ) 20.07 Outstanding at September 30, 2019 15,227 $ 16.64

Variable Interest Entity (Table

Variable Interest Entity (Tables)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Variable Interest Entity	The financial position of Mardi Gras at September 30, 2019 and December 31, 2018 , its financial performance for the three and six months ended September 30, 2019 and 2018 and cash flows for the nine months ended September 30, 2019 and 2018, as reflected in our condensed consolidated financial statements, are as follows: September 30, 2019 December 31, 2018 Balance sheet Equity method investments $ 394,500 $ 402,783 Non-controlling interests 138,075 140,974 Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Statement of operations Income from equity method investments $ 13,255 $ 10,340 $ 37,055 $ 35,205 Less: Net income attributable to non-controlling interests 4,639 8,272 12,969 28,163 Net impact on Net income attributable to the Partnership $ 8,616 $ 2,068 $ 24,086 $ 7,042 Nine Months Ended September 30, 2019 2018 Statement of cash flows Cash flows from operating activities Distributions of earnings received from equity method investments $ 37,055 $ 35,205 Cash flows from investing activities Distribution in excess of earnings from equity method investments 8,283 15,362 Cash flows from financing activities Distributions to non-controlling interests (15,868 ) (40,453 ) Net change on the Partnership's cash and cash equivalents $ 29,470 $ 10,114

Business and Basis of Present_3

Business and Basis of Presentation (Details) $ in Millions	Oct. 01, 2018USD ($)	Sep. 30, 2019segment	Sep. 30, 2018
Variable Interest Entity [Line Items]
Payments to acquire equity method investments | $	$ 468
Number of reportable segments | segment		1
KM Phoenix
Variable Interest Entity [Line Items]
Percentage Ownership		25.00%
Total Mardi Gras Joint Ventures
Variable Interest Entity [Line Items]
Additional interest acquired (as a percent)	45.00%
Percentage Ownership	65.00%	65.00%	20.00%
KM Phoenix
Variable Interest Entity [Line Items]
Percentage Ownership	25.00%	25.00%
Ursa
Variable Interest Entity [Line Items]
Percentage Ownership	22.70%	22.70%
Mars
Variable Interest Entity [Line Items]
Percentage Ownership		28.50%	28.50%
Caesar
Variable Interest Entity [Line Items]
Percentage Ownership		56.00%	56.00%
Cleopatra
Variable Interest Entity [Line Items]
Percentage Ownership		53.00%	53.00%
Proteus
Variable Interest Entity [Line Items]
Percentage Ownership		65.00%	65.00%
Endymion
Variable Interest Entity [Line Items]
Percentage Ownership		65.00%	65.00%

Revenue Recognition - Narrative

Revenue Recognition - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Income related to FLA arrangements with Parent	$ 2,728	$ 2,691	$ 7,824	$ 7,691

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Transportation services revenue - third parties	$ 725	$ 508	$ 2,238	$ 2,072
Transportation services revenue - related parties	33,836	31,566	91,164	85,556
Total revenue	$ 34,561	$ 32,074	$ 93,402	$ 87,628

Revenue Recognition - Remaining

Revenue Recognition - Remaining Performance Obligation, Expected Timing of Satisfaction (Details) $ in Thousands	Sep. 30, 2019USD ($)
Revenue from Contract with Customer [Abstract]
Unfulfilled performance obligations	$ 138,642
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Revenue from Contract with Customer [Abstract]
Unfulfilled performance obligations	$ 29,052
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue from Contract with Customer [Abstract]
Unfulfilled performance obligations	$ 109,590
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year

Revenue Recognition - Contract

Revenue Recognition - Contract with Customer, Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables from contracts with customers	$ 491	$ 325
Third parties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables from contracts with customers	491	325
Related parties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables from contracts with customers	10,793	9,611
Deferred revenue and credits	$ 3,026	$ 1,067

Leases - Summary of Balance She

Leases - Summary of Balance Sheet Information (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Leases [Abstract]
ROU Assets	$ 481	$ 518
Current lease liability	60	60	$ 0
Long-term lease liability	$ 427	$ 458

Leases - Narrative (Details)

Leases - Narrative (Details)	9 Months Ended
	Sep. 30, 2019lease
Lessee, Lease, Description [Line Items]
Number of operating leases	4
Annual escalation, percentage	3.00%
Weighted average discount rate	4.36%
Weighted average remaining lease term	15 years 4 months 24 days
Expiring in 2036
Lessee, Lease, Description [Line Items]
Number of operating leases	2
Expiring in 2020
Lessee, Lease, Description [Line Items]
Number of operating leases	2
Right of Renewal and Annual Escalation
Lessee, Lease, Description [Line Items]
Number of operating leases	2
Non-Lease Component For Maintenance Expense
Lessee, Lease, Description [Line Items]
Number of operating leases	2

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Leases [Abstract]
2019	$ 16
2020	63
2021	32
2022	33
2023	34
Thereafter	514
Total	$ 692
2019		$ 62
2020		63
2021		32
2022		33
2023		34
Thereafter		514
Total		$ 738

Equity Method Investments - Nar

Equity Method Investments - Narrative (Details) - USD ($)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Impairment loss on equity method investments	$ 0	$ 0

Equity Method Investments - Sch

Equity Method Investments - Schedule of Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Oct. 01, 2018
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Distributions Received	$ (32,462)	$ (27,816)	$ (94,776)	$ (86,676)
Cumulative Effect of Accounting Change				(2,746)
Income from EMI	30,104	22,581	83,312	66,262
Equity method investments	537,575	464,839	537,575	464,839	$ 549,039
Statement of operations
Revenues	146,090	124,644	410,232	339,931
Operating expenses	63,313	53,994	180,277	147,024
Net income	$ 83,039	$ 70,761	$ 231,413	$ 193,248
Mars
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Percentage Ownership	28.50%	28.50%	28.50%	28.50%
Distributions Received	$ (14,250)	$ (13,167)	$ (40,088)	$ (36,110)
Cumulative Effect of Accounting Change				(2,746)
Income from EMI	14,104	12,241	37,819	31,057
Equity method investments	$ 56,874	$ 57,762	$ 56,874	$ 57,762
Caesar
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Percentage Ownership	56.00%	56.00%	56.00%	56.00%
Distributions Received	$ (4,760)	$ (4,760)	$ (14,448)	$ (15,357)
Cumulative Effect of Accounting Change				0
Income from EMI	3,640	4,519	13,461	12,364
Equity method investments	$ 118,403	$ 120,593	$ 118,403	$ 120,593
Cleopatra
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Percentage Ownership	53.00%	53.00%	53.00%	53.00%
Distributions Received	$ (2,438)	$ (2,544)	$ (9,063)	$ (7,844)
Cumulative Effect of Accounting Change				0
Income from EMI	1,703	1,306	7,079	4,641
Equity method investments	$ 117,566	$ 120,309	$ 117,566	$ 120,309
Proteus
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Percentage Ownership	65.00%	65.00%	65.00%	65.00%
Distributions Received	$ (4,342)	$ (3,510)	$ (11,882)	$ (13,585)
Cumulative Effect of Accounting Change				0
Income from EMI	3,153	2,135	7,085	9,047
Equity method investments	$ 76,535	$ 82,606	$ 76,535	$ 82,606
Endymion
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Percentage Ownership	65.00%	65.00%	65.00%	65.00%
Distributions Received	$ (3,510)	$ (3,835)	$ (9,945)	$ (13,780)
Cumulative Effect of Accounting Change				0
Income from EMI	4,759	2,380	9,430	9,153
Equity method investments	81,996	$ 83,569	81,996	$ 83,569
Others
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Percentage Ownership		0.00%		0.00%
Distributions Received	(3,162)	$ 0	(9,350)	$ 0
Cumulative Effect of Accounting Change				0
Income from EMI	2,745	0	8,438	0
Equity method investments	$ 86,201	$ 0	$ 86,201	$ 0
Total Mardi Gras Joint Ventures
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Percentage Ownership	65.00%	20.00%	65.00%	20.00%		65.00%
Ursa
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Percentage Ownership	22.70%		22.70%			22.70%
KM Phoenix
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Percentage Ownership	25.00%		25.00%			25.00%

Property, Plant and Equipment_2

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 105,795	$ 105,795	$ 107,970
Less: Accumulated depreciation	(40,929)	(40,929)	(39,390)
Property, plant and equipment, net	64,866	64,866	68,580
Impairment charge	0	2,300
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment	155	155	155
Rights-of-way
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,380	1,380	1,380
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	9,332	9,332	12,032
Pipeline and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	93,951	93,951	93,617
Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment	514	514	509
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 463	$ 463	$ 277

Other Current Liabilities (Deta

Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Current portion of environmental remediation obligations	$ 620		$ 629
Current portion of lease liabilities	60	$ 60	0
Accrued interest payable - related parties	4,155		4,155
Accrued liabilities	1,912		2,116
Other current liabilities	$ 6,747		$ 6,900

Debt (Details)

Debt (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	May 03, 2019	Feb. 20, 2019	Dec. 31, 2018	Oct. 01, 2018	Oct. 30, 2017
Line of Credit Facility [Line Items]
Weighted average interest rate	3.25%	2.24%	3.25%	2.24%
Line of Credit | Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility maximum borrowing capacity									$ 600,000,000
Outstanding borrowing	$ 468,000,000	$ 468,000,000	$ 468,000,000	$ 468,000,000	$ 468,000,000	$ 468,000,000	$ 468,000,000	$ 468,000,000
Interest expense	$ 4,100,000	$ 200,000	$ 12,300,000	$ 600,000
Commitment fee percentage			0.10%
Utilization fee percentage			0.20%

Related Party Transactions - Na

Related Party Transactions - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Related parties	$ 33,836,000	$ 31,566,000	$ 91,164,000	$ 85,556,000
Deferred revenue and credits	3,026,000		$ 3,026,000			$ 1,067,000
Parent
Related Party Transaction [Line Items]
Performance or restricted period			3 years
BP Products
Related Party Transaction [Line Items]
Deficiency revenue	$ 2,356,000	$ 3,857,000	$ 2,356,000	$ 3,857,000
BP Pipelines
Related Party Transaction [Line Items]
Annual fee paid to related party						$ 13,300,000
Scenario, Forecast | BP Pipelines
Related Party Transaction [Line Items]
Annual fee paid to related party					$ 13,600,000
Mardi Gras Transportation System Company LLC
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by Parent	35.00%	80.00%	35.00%	80.00%

Related Party Transactions - Sc

Related Party Transactions - Schedule of Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Related Party Transactions [Abstract]
Operating expenses—related parties	$ 1,423	$ 1,506	$ 4,317	$ 3,494
Maintenance expenses—related parties	66	31	139	75
General and administrative—related parties	3,476	3,691	10,597	10,556
Total costs and expenses—related parties	$ 4,965	$ 5,228	$ 15,053	$ 14,125

Net Income Per Limited Partne_3

Net Income Per Limited Partner Unit - Schedule of Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 14, 2019	Oct. 17, 2019	Aug. 14, 2019	May 15, 2019	Nov. 15, 2018	Aug. 15, 2018	May 15, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Distribution Made to Limited Partner [Line Items]
Partner distributions declared			$ 34,315	$ 32,946	$ 30,536	$ 28,543	$ 28,021	$ 35,891	$ 30,536	$ 103,152	$ 87,100
Dividends declared per share (in dollars per share)			$ 0.3237	$ 0.3126	$ 0.2915	$ 0.2725	$ 0.2675
General Partner
Distribution Made to Limited Partner [Line Items]
Partner distributions declared			$ 403	$ 198	$ 0	$ 0	$ 0	743	0	1,344	0
Limited Partners Common Units
Distribution Made to Limited Partner [Line Items]
Partner distributions declared			16,958	16,375	15,268	14,272	14,010	17,576	15,268	50,909	43,550
Limited Partners Subordinated Units
Distribution Made to Limited Partner [Line Items]
Partner distributions declared			$ 16,954	$ 16,373	$ 15,268	$ 14,271	$ 14,011	$ 17,572	$ 15,268	$ 50,899	$ 43,550
Subsequent Event
Distribution Made to Limited Partner [Line Items]
Partner distributions declared	$ 35,891
Dividends declared per share (in dollars per share)	$ 0.3355	$ 0.3355
Subsequent Event | General Partner
Distribution Made to Limited Partner [Line Items]
Partner distributions declared	$ 743
Subsequent Event | Limited Partners Common Units
Distribution Made to Limited Partner [Line Items]
Partner distributions declared	17,576
Subsequent Event | Limited Partners Subordinated Units
Distribution Made to Limited Partner [Line Items]
Partner distributions declared	$ 17,572

Net Income Per Limited Partne_4

Net Income Per Limited Partner Unit - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	Aug. 14, 2019	May 15, 2019	Nov. 15, 2018	Aug. 15, 2018	May 15, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Partner distributions declared	$ 34,315	$ 32,946	$ 30,536	$ 28,543	$ 28,021	$ 35,891	$ 30,536	$ 103,152	$ 87,100
Net income attributable to the Partnership in excess of distributions						9,863	4,683	17,086	9,128
Net income attributable to the Partnership						$ 45,754	$ 35,219	$ 120,238	$ 96,228
Weighted average units outstanding (in millions):
Basic and Diluted (in shares)						104.8	104.8	104.8	104.8
Incentive distribution rights currently held by the General Partner
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Partner distributions declared	403	198	0	0	0	$ 743	$ 0	$ 1,344	$ 0
Net income attributable to the Partnership in excess of distributions						0	0	0	0
Net income attributable to the Partnership						743	0	1,344	0
Limited partners' distribution declared on common units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Partner distributions declared	16,958	16,375	15,268	14,272	14,010	17,576	15,268	50,909	43,550
Net income attributable to the Partnership in excess of distributions						4,932	2,341	8,544	4,564
Net income attributable to the Partnership						$ 22,508	$ 17,609	$ 59,453	$ 48,114
Weighted average units outstanding (in millions):
Basic and Diluted (in shares)						52.4	52.4	52.4	52.4
Net income per limited partner unit (in dollars):
Basic and Diluted (in dollars per share)						$ 0.43	$ 0.34	$ 1.13	$ 0.92
Limited partners' distribution declared on subordinated units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Partner distributions declared	$ 16,954	$ 16,373	$ 15,268	$ 14,271	$ 14,011	$ 17,572	$ 15,268	$ 50,899	$ 43,550
Net income attributable to the Partnership in excess of distributions						4,931	2,342	8,542	4,564
Net income attributable to the Partnership						$ 22,503	$ 17,610	$ 59,441	$ 48,114
Weighted average units outstanding (in millions):
Basic and Diluted (in shares)						52.4	52.4	52.4	52.4
Net income per limited partner unit (in dollars):
Basic and Diluted (in dollars per share)						$ 0.43	$ 0.34	$ 1.13	$ 0.92

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2019	Dec. 31, 2018	Oct. 01, 2018	Sep. 30, 2018
Site Contingency [Line Items]
Environmental liability indemnification cap	$ 25,000,000		$ 25,000,000
Other matters indemnification cap	15,000,000		15,000,000
Aggregate deductible	500,000		500,000
Environmental liabilities	3,760,000		3,760,000	$ 3,853,000
Indemnification assets	3,760,000		3,760,000	$ 3,853,000
Impairment charge	0		2,300,000
Response expense	500,000	$ 800,000	1,300,000
Insurance deductible			1,000,000
Accrued insurance recovery	$ 2,600,000		$ 2,600,000
Mars
Site Contingency [Line Items]
Percentage Ownership	28.50%		28.50%			28.50%
Mardi Gras Transportation System Company LLC
Site Contingency [Line Items]
Percentage Ownership	65.00%		65.00%		65.00%	20.00%
Caesar
Site Contingency [Line Items]
Percentage Ownership	56.00%		56.00%			56.00%
Cleopatra
Site Contingency [Line Items]
Percentage Ownership	53.00%		53.00%			53.00%
Endymion
Site Contingency [Line Items]
Percentage Ownership	65.00%		65.00%			65.00%
Proteus
Site Contingency [Line Items]
Percentage Ownership	65.00%		65.00%			65.00%
Ursa
Site Contingency [Line Items]
Percentage Ownership	22.70%		22.70%		22.70%
KM Phoenix
Site Contingency [Line Items]
Percentage Ownership	25.00%		25.00%		25.00%

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Balance Sheet Classification of Environmental Liabilities and Indemnification Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Current portion of environmental remediation obligations	$ 620	$ 629
Long-term portion of environmental remediation obligations	3,140	3,224
Total	3,760	3,853
Current portion of indemnification assets	620	629
Non-current portion of indemnification assets	3,140	3,224
Total	$ 3,760	$ 3,853

Unit-Based Compensation - Narra

Unit-Based Compensation - Narrative (Details) - Phantom Share Units (PSUs) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense	$ 64	$ 56	$ 175	$ 140
Unrecognized compensation cost related to phantom unit awards	$ 105		$ 105
Weighted average recognition period			4 months 24 days
BP Midstream Partners LP 2017 Long Term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum aggregate number of common units that may be issued (in shares)	5,502,271		5,502,271

Unit-Based Compensation - Phant

Unit-Based Compensation - Phantom Units Activity (Details) - Phantom Share Units (PSUs)	9 Months Ended
	Sep. 30, 2019$ / sharesshares
Number of Units (in units)
Beginning balance outstanding (shares) | shares	3,737
Granted (in shares) | shares	15,227
Vested (in shares) | shares	(3,737)
Ending balance outstanding (shares) | shares	15,227
Weighted Average Grant Date Fair Value per Unit (in dollars)
Beginning balance outstanding (in dollars per share) | $ / shares	$ 20.07
Granted (in dollars per share) | $ / shares	16.64
Vested (in dollars per share) | $ / shares	20.07
Ending balance outstanding (in dollars per share) | $ / shares	$ 16.64

Variable Interest Entity (Detai

Variable Interest Entity (Details) - USD ($)	Oct. 01, 2018	Oct. 30, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Balance sheet
Equity method investments			$ 537,575,000	$ 464,839,000	$ 537,575,000	$ 464,839,000	$ 549,039,000
Non-controlling interests			138,075,000		138,075,000		140,974,000
Statement of operations
Income from equity method investments			30,104,000	22,581,000	83,312,000	66,262,000
Less: Net income attributable to non-controlling interests			4,639,000	8,272,000	12,969,000	28,163,000
Net income attributable to the Partnership			45,754,000	$ 35,219,000	120,238,000	96,228,000
Cash flows from operating activities
Distributions of earnings received from equity method investments					86,481,000	71,314,000
Cash flows from financing activities
Distributions to non-controlling interests					(15,868,000)	$ (40,453,000)
Mardi Gras Transportation System Company LLC
Variable Interest Entity [Line Items]
Non-controlling interest (as a percent)	35.00%			80.00%		80.00%
Mardi Gras Transportation System Company LLC | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Economic interest (as a percent)		20.00%
Managing member interest (as a percent)		100.00%
Remainder of economic interest held in VIE (as a percent)		79.00%
Remainder of economic interest held by affiliate (as a percent)		1.00%
Mardi Gras Transportation System Company LLC
Variable Interest Entity [Line Items]
Additional interest acquired (as a percent)	45.00%
Mardi Gras Transportation System Company LLC | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets of VIE			0		0		0
Balance sheet
Equity method investments			394,500,000		394,500,000		402,783,000
Non-controlling interests			138,075,000		138,075,000		$ 140,974,000
Statement of operations
Income from equity method investments			13,255,000	$ 10,340,000	37,055,000	$ 35,205,000
Less: Net income attributable to non-controlling interests			4,639,000	8,272,000	12,969,000	28,163,000
Net income attributable to the Partnership			$ 8,616,000	$ 2,068,000	24,086,000	7,042,000
Cash flows from operating activities
Distributions of earnings received from equity method investments					37,055,000	35,205,000
Cash flows from investing activities
Distribution in excess of earnings from equity method investments					8,283,000	15,362,000
Cash flows from financing activities
Distributions to non-controlling interests					(15,868,000)	(40,453,000)
Net change in cash and cash equivalents					$ 29,470,000	$ 10,114,000

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	Nov. 14, 2019	Oct. 17, 2019	Aug. 14, 2019	May 15, 2019	Nov. 15, 2018	Aug. 15, 2018	May 15, 2018
Subsequent Event [Line Items]
Dividends declared per share (in dollars per share)			$ 0.3237	$ 0.3126	$ 0.2915	$ 0.2725	$ 0.2675
Scenario, Forecast
Subsequent Event [Line Items]
Total distribution paid	$ 35.9
Dividends paid to non-affiliated common unitholders	16
Net transfers to Parent	19.9
Incentive distribution rights	$ 0.7
Subsequent Event
Subsequent Event [Line Items]
Dividends declared per share (in dollars per share)	$ 0.3355	$ 0.3355