Quarterly Financial Data (Unaudited) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data [Line Items]
Total revenues	$ 495,078		$ 313,849		$ 292,934		$ 277,078		$ 328,078		$ 260,943		$ 247,242		$ 236,959		$ 1,378,939	$ 1,073,222	$ 608,447
Gross profit	374,577	[1]	197,197	[1]	195,411	[1]	184,165	[1]	238,502	[1]	177,410	[1]	164,398	[1]	154,196	[1]
Net income	239,472		51,902		72,468		65,529		130,815		79,211		70,427		60,696		429,371	341,149	178,387
Net income	$ 228,310		$ 41,218		$ 67,454		$ 61,078		$ 129,057		$ 78,217		$ 69,213		$ 59,538		$ 398,060	$ 336,025	$ 178,455
Common Units
Quarterly Financial Data [Line Items]
Net income per limited partner unit - basic and diluted (Note 4)	$ 0.65		$ 0.03		$ 0.18		$ 0.15		$ 0.44		$ 0.21		$ 0.17		$ 0.13
Subordinated units
Quarterly Financial Data [Line Items]
Net income per limited partner unit - basic and diluted (Note 4)											$ 0.33		$ 0.31		$ 0.29

[1] Total revenue less operating costs.