Fair Value of Financial Instruments - Derivative Contract Positions (Details) bbl in Thousands, $ in Thousands	Jun. 30, 2019 USD ($) bbl	Mar. 31, 2019 USD ($) bbl
Fair value of financial instruments
Fair Value of Net Assets (Liabilities)	$ 45,968	$ 28,457
Net cash collateral held	(15,915)	(18,479)
Net commodity derivative asset	30,053	9,978
Crude oil fixed-price
Fair value of financial instruments
Fair Value of Net Assets (Liabilities)	$ 2,580	$ 1,014
Crude oil fixed-price \| Short
Fair value of financial instruments
Net Long (Short) Notional Units (in barrels) \| bbl	(2,200)	(1,961)
Propane fixed-price
Fair value of financial instruments
Fair Value of Net Assets (Liabilities)	$ (2,430)	$ 608
Propane fixed-price \| Long
Fair value of financial instruments
Net Long (Short) Notional Units (in barrels) \| bbl	947	198
Refined products fixed-price
Fair value of financial instruments
Fair Value of Net Assets (Liabilities)	$ 45,692	$ 22,079
Refined products fixed-price \| Short
Fair value of financial instruments
Net Long (Short) Notional Units (in barrels) \| bbl	(4,623)	(2,296)
Other
Fair value of financial instruments
Fair Value of Net Assets (Liabilities)	$ 126	$ 4,756

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

The amount of the obligation to return cash collateral or right to reclaim cash collateral under master netting arrangements.

+ References

No definition available.

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Fair value as of the balance sheet date of price risk derivative assets, net of price risk derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized on the balance sheet.

+ References

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