Variable Interest Entity and Equity Method Investment (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2012 As previously reported	Jun. 30, 2012 As previously reported	Dec. 31, 2012 As previously reported
Statement of cash flows
Net income	$ 85,498	$ 186,533	$ 64,367	$ 202,307	$ 187,136	$ 203,409
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	71,562	41,336	139,579	80,918	42,918	84,063
Accretion of asset retirement obligations	157	160	509	396	161	399
Equity in (earnings) loss of unconsolidated affiliate	(430)	(1,109)	(665)	(1,548)	(551)	(542)
Distributions from unconsolidated affiliate			2,728	4,566		1,700
Receivables			(34,529)	90,337		90,664
Other current assets			607	2,638		2,738
Accounts payable and accrued liabilities			(7,462)	(71,783)		(71,784)
Net cash provided by operating activities			177,596	253,621		256,437
Cash flows from investing activities:
Capital expenditures			(1,435,084)	(580,980)		(582,203)
Investment in unconsolidated affiliates			(8,336)	(839)
Net cash flows used in investing activities			(1,435,021)	(1,087,114)		(1,087,498)
Cash flows from financing activities:
Contributions from non-controlling interest			685,219	1,101		1,940
Payment of distributions to non-controlling interest			(112)	(71)		(2,937)
Net cash flows provided by financing activities			1,266,223	841,534		839,507
Net increase in cash and cash equivalents			8,798	8,041		8,446
Cash and cash equivalents at beginning of year			345,756	114,332		117,016	347,899
Cash and cash equivalents at end of period	$ 354,554	$ 122,373	$ 354,554	$ 122,373	$ 125,462	$ 125,462	$ 347,899