Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income (loss)	$ 63,625	$ 67,596	$ (42,727)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	26,912	20,187	16,515
Reserve for doubtful accounts	(1)	88	0
Amortization of loan fees	1,271	523	109
Unit-based compensation expense	2,000	1,564	49
Loss (gain) and impairments on disposal of assets, net	(278)	157	0
Accounts receivable - Third-party	(267)	(54,377)	(105)
Accounts receivable - Affiliate	8,042	(40,625)	(11,431)
Inventories	(717)	1,799	(2,585)
Prepaid expenses	4,143	(1,466)	769
Other assets	(2,823)	(3,501)	(3,823)
Accounts payable and accrued liabilities	(6,112)	122,860	6,912
Other long-term liabilities	9	(5)	5
Net cash provided by (used in) operating activities	95,804	114,800	(36,312)
Cash flows from investing activities:
Capital expenditures	(62,995)	(79,172)	(84,825)
Proceeds from sale of assets	506	106	36
Net cash used in investing activities	(62,489)	(79,066)	(84,789)
Cash flows from financing activities:
Additions to long-term debt	300,000	0	0
Payments on revolving credit facility	(269,000)	0	0
Borrowings on revolving credit facility	145,000	269,000	0
Quarterly distribution to Western	(45,455)	(35,042)	0
Quarterly distribution to non-controlling interest holders	22,629	18,394	0
Proceeds from issuance of common units, net of underwriters' discount and commissions	0	0	325,263
Offering costs for issuance of common units	0	0	(2,117)
Deferred financing costs	(6,820)	0	(2,616)
Contributions from affiliate	25,896	38,996	129,454
Distribution to Western due to acquisitions	(170,000)	(320,000)	(244,884)
Net cash provided by (used in) financing activities	(43,008)	(65,440)	205,100
Net change in cash and cash equivalents	(9,693)	(29,706)	83,999
Cash and cash equivalents at beginning of year	54,298	84,004	5
Cash and cash equivalents at end of year	$ 44,605	$ 54,298	$ 84,004