Transactions with Affiliates - Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2017
Transactions with Affiliates
Accounts receivable-affiliates	$ 4,772	$ 6,711
Accounts payable-affiliates	1,254	7,918
Equity in earnings of unconsolidated entities	7,964	3,084	$ 16,121
SemGroup
Transactions with Affiliates
Sales to related party	606	3,866	43,825
Purchases from related party	5,034	12,254	53,209
Accounts receivable-affiliates	49	6,668
Accounts payable-affiliates	0	6,571
NGL Energy Holdings LLC
Transactions with Affiliates
Accounts receivable-affiliates	4,693	0
Equity method investees
Transactions with Affiliates
Sales to related party	294	692	14,836
Purchases from related party	66,820	121,336	113,780
Accounts receivable-affiliates	6	15
Accounts payable-affiliates	8	1,306
Equity method investees \| Loan agreement
Transactions with Affiliates
Loan receivable from Victory Propane, LLC	1,200	3,200		$ 4,200
Equity in earnings of unconsolidated entities	$ 300
Loan agreement successive extension period	1 year
Entities affiliated with management
Transactions with Affiliates
Increase in property, plant and equipment	$ 800
Sales to related party	268	290	318
Purchases from related party	3,870	15,209	$ 45,197
Accounts receivable-affiliates	24	28
Accounts payable-affiliates	$ 1,246	$ 41

Related Party Transaction, Loan Agreement Extension Period

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The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle).

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Carrying amount as of the balance sheet date of obligations due all related parties. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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Amounts due from parties associated with the reporting entity as evidenced by a written promise to pay, due after 1 year (or 1 business cycle).

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Amount of acquisition of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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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.

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Purchases during the period (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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