Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Tax
Income before provision for income tax	$ 10,108	$ 101,781	$ 38,570	$ 87,207
Federal income tax at statutory rate			2,324	18,494
Permanent items			33	29
State income taxes, net of federal benefit			577	1,482
Federal and state tax rate change			4,250
Provision on income from Class A units			2,422	2,835
Total provision for income tax	(2,940)	16,283	9,606	22,840
Elimination
Income Tax
Income before provision for income tax			(368)	(5,655)
Federal statutory income tax rate (as a percent)			0.00%	0.00%
Corporation | Reportable entities
Income Tax
Income before provision for income tax			6,641	52,839
Federal statutory income tax rate (as a percent)			35.00%	35.00%
Federal income tax at statutory rate			2,324	18,494
Permanent items			33	29
State income taxes, net of federal benefit			168	1,321
Federal and state tax rate change			4,250
Provision on income from Class A units			2,422	2,835
Total provision for income tax			9,197	22,679
Partnership | Reportable entities
Income Tax
Income before provision for income tax			32,297	40,023
Federal statutory income tax rate (as a percent)			0.00%	0.00%
State income taxes, net of federal benefit			409	161
Total provision for income tax			$ 409	$ 161