Income Taxes (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Tax Cuts and Jobs Act of 2017, incomplete accounting, change in tax rate, deferred tax asset, provisional income tax expense	$ 27,500
Tax Cuts and Jobs Act of 2017, incomplete accounting, valuation allowance, deferred tax asset, decrease, amount	30,200
Tax Cuts and Jobs Act of 2017, incomplete accounting, change in tax rate, deferred tax liability, provisional income tax benefit	2,800
Tax Cuts and Jobs Act of 2017, incomplete accounting, transition tax for AMT, provisional income tax benefit	300
Effective rate		8.70%	4.50%	6.80%	6.80%
Provision for income taxes		$ (6,637)	$ (10,755)	$ 23,475
Net operating loss carryforwards	207,600	207,600
Unrecognized tax benefits that would not impact effective tax rate	800	$ 800
Tax receivable agreement, percent of cash savings paid to shareholders		85.00%
Tax receivable agreement, percent of cash savings not paid to shareholders		15.00%
Periods Prior to June 2015
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 79,300	$ 79,300