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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share Basic [Line Items]
Net income (loss)	$ (8,371)	$ 95,087	$ 67,741	$ 104,104
Distributions on Series B cumulative convertible preferred units	(5,250)	(5,250)	(10,500)	(10,500)
NET INCOME (LOSS) ATTRIBUTABLE TO THE GENERAL PARTNER AND COMMON AND SUBORDINATED UNITS	(13,621)	89,837	57,241	93,604
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	(13,621)	89,837	57,241	93,604
Common Units
ALLOCATION OF NET INCOME (LOSS):
Allocation of net income (loss)	$ (13,621)	$ 67,718	$ 57,241	$ 69,611
Weighted average common units outstanding:
Weighted average units outstanding (basic) (in shares)	206,707	150,101	206,669	129,873
Effect of dilutive securities (in shares)	0	14,969	0	0
Weighted average units outstanding (diluted) (in shares)	206,707	165,070	206,669	129,873
NET INCOME (LOSS) ATTRIBUTABLE TO LIMITED PARTNERS PER COMMON AND SUBORDINATED UNIT:
Per unit (basic) (in dollars per share)	$ (0.07)	$ 0.45	$ 0.28	$ 0.54
Per unit (diluted) (in dollars per share)	$ (0.07)	$ 0.44	$ 0.28	$ 0.54
Subordinated units
ALLOCATION OF NET INCOME (LOSS):
Allocation of net income (loss)	$ 0	$ 22,119	$ 0	$ 23,993
Weighted average common units outstanding:
Weighted average units outstanding (basic) (in shares)	0	56,104	0	76,105
Effect of dilutive securities (in shares)	0	0	0	0
Weighted average units outstanding (diluted) (in shares)	0	56,104	0	76,105
NET INCOME (LOSS) ATTRIBUTABLE TO LIMITED PARTNERS PER COMMON AND SUBORDINATED UNIT:
Per unit (basic) (in dollars per share)	$ 0	$ 0.39	$ 0	$ 0.32
Per unit (diluted) (in dollars per share)	$ 0	$ 0.39	$ 0	$ 0.32