Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Income Tax
Income before provision for income tax	$ 28,462	$ (14,574)
Federal income tax at statutory rate	6,461	7,109
Permanent items	21	16
State income taxes, net of federal benefit	619	375
Federal and state tax rate change	4,250
Provision on income from Class A units	1,195	(943)
Total provision for income tax	12,546	6,557
Elimination
Income Tax
Income before provision for income tax	(5,103)	(1,438)
Federal statutory income tax rate (as a percent)	0.00%	0.00%
Corporation | Reportable entities
Income Tax
Income before provision for income tax	18,459	20,311
Federal statutory income tax rate (as a percent)	35.00%	35.00%
Federal income tax at statutory rate	6,461	7,109
Permanent items	21	16
State income taxes, net of federal benefit	463	508
Federal and state tax rate change	4,250
Provision on income from Class A units	1,195	(943)
Total provision for income tax	12,390	6,690
Partnership | Reportable entities
Income Tax
Income before provision for income tax	15,106	(33,447)
Federal statutory income tax rate (as a percent)	0.00%	0.00%
State income taxes, net of federal benefit	156	(133)
Total provision for income tax	$ 156	$ (133)