Transactions with Affiliates (Details) - Entity [Domain] - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015
Transactions with Affiliates
Accounts receivable from affiliates	$ 18,740		$ 17,198
Accounts payable to affiliates	25,592		25,794
SemGroup
Transactions with Affiliates
Sales to related party	37,438	$ 25,982
Purchase from related party	38,825	39,120
Accounts receivable from affiliates	17,975		13,443
Accounts payable to affiliates	17,391		11,546
Equity method investees
Transactions with Affiliates
Sales to related party	1,390
Purchase from related party	30,948	36,276
Accounts receivable from affiliates	713		652
Accounts payable to affiliates	4,649		6,788
Loan receivable	23,800
Entities affiliated with management
Transactions with Affiliates
Increase in property, plant and equipment	7,000
Sales to related party	107	148
Purchase from related party	7,180	$ 3,139
Accounts receivable from affiliates	52		3,103
Accounts payable to affiliates	$ 3,552		$ 7,460