Earnings Per Unit - Computation of Basic and Diluted Earnings per Unit (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share Basic [Line Items]
Net income (loss)	$ 54,174	$ (20,810)	$ 115,757	$ (10,061)
NET (INCOME) LOSS ATTRIBUTABLE TO NONCONTROLLING INTERESTS	16	9	7	7
DISTRIBUTIONS ON REDEEMABLE PREFERRED UNITS	(672)	(1,310)	(1,786)	(3,114)
NET INCOME (LOSS) ATTRIBUTABLE TO THE GENERAL PARTNER AND COMMON AND SUBORDINATED UNITS	53,518	(22,111)	113,978	(13,168)
ALLOCATION OF NET INCOME (LOSS):
General partner interest	0	0	0	0
NET INCOME (LOSS) ATTRIBUTABLE TO THE GENERAL PARTNER AND COMMON AND SUBORDINATED UNITS	53,518	(22,111)	113,978	(13,168)
Common Units
ALLOCATION OF NET INCOME (LOSS):
Allocation of net income (loss)	$ 32,100	$ (7,445)	$ 67,617	$ 862
NET INCOME (LOSS) ATTRIBUTABLE TO LIMITED PARTNERS PER COMMON AND SUBORDINATED UNIT:
Per unit (basic) (in dollars per share)	$ 0.33	$ (0.08)	$ 0.69	$ 0.01
Weighted average units outstanding (basic) (in shares)	97,990	96,356	97,448	96,418
Per unit (diluted) (in dollars per share)	$ 0.33	$ (0.08)	$ 0.69	$ 0.01
Weighted average units outstanding (diluted) (in shares)	97,990	96,418	97,448	96,481
Subordinated Units
ALLOCATION OF NET INCOME (LOSS):
Allocation of net income (loss)	$ 21,418	$ (14,666)	$ 46,361	$ (14,030)
NET INCOME (LOSS) ATTRIBUTABLE TO LIMITED PARTNERS PER COMMON AND SUBORDINATED UNIT:
Per unit (basic) (in dollars per share)	$ 0.22	$ (0.15)	$ 0.49	$ (0.15)
Weighted average units outstanding (basic) (in shares)	95,388	95,189	95,269	95,092
Per unit (diluted) (in dollars per share)	$ 0.22	$ (0.15)	$ 0.49	$ (0.15)
Weighted average units outstanding (diluted) (in shares)	95,388	95,092	95,269	95,092