Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Tax
Income before provision for income tax	$ (30,283)	$ (22,685)	$ 56,924	$ 228,640
Federal income tax at statutory rate			8,918	26,138
Permanent items			25	21
State income taxes, net of federal benefit			665	4,152
Provision on income from Class A units			2,976	11,287
Total provision for income tax	(10,256)	(7,420)	12,584	41,598
Corporation
Income Tax
Income before provision for income tax			25,480	74,679
Federal statutory income tax rate (as a percent)			35.00%	35.00%
Federal income tax at statutory rate			8,918	26,138
Permanent items			25	21
State income taxes, net of federal benefit			511	3,418
Provision on income from Class A units			2,976	11,287
Total provision for income tax			12,430	40,864
Partnership
Income Tax
Income before provision for income tax			40,223	151,752
Federal statutory income tax rate (as a percent)			0.00%	0.00%
State income taxes, net of federal benefit			154	734
Total provision for income tax			154	734
Eliminations
Income Tax
Income before provision for income tax			$ (8,779)	$ 2,209
Federal statutory income tax rate (as a percent)			0.00%	0.00%