Net Income Per Limited Partner Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net income per limited partner unit
Net income	$ 87,175	$ 49,912	$ 162,267	$ 92,829
Net income attributable to incentive distribution rights	(15,328)	(2,731)	(26,881)	(4,581)
Limited partners' interest in net income	$ 71,847	$ 47,181	$ 135,386	$ 88,248
Net income per limited partner unit - basic	$ 0.39	$ 0.27	$ 0.73	$ 0.50
Net income per limited partner unit - diluted	$ 0.39	$ 0.27	$ 0.73	$ 0.50
Weighted average limited partner units outstanding - basic	186,065,000	176,172,000	184,558,000	176,167,000
Weighted average limited partner units outstanding - diluted	186,533,000	176,226,000	185,002,000	176,203,000
Phantom share units
Net income per limited partner unit
Weighted average limited partner units outstanding - diluted	467,540		443,981
Common units
Net income per limited partner unit
Weighted average limited partner units outstanding - diluted	186,532,700		185,001,686