Income Taxes - (Details 5) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Loss Carryforwards [Line Items]
Valuation Allowance, Deferred Tax Asset, Change in Amount	$ 100,000
Operating Loss Carryforwards Utilized During Period	154,400,000
Income Taxes (Textual) [Abstract]
Net deferred tax expense resulting from intercompany sale of tax credit business	6,500,000
Portion of unrecognized tax benefit that, if recognized, would impact the effective tax rate	2,200,000
Excess tax benefits recognized related to employee stock option exercises and vested restricted stock awards	800,000	600,000
Consolidated income (loss) subject to tax	137,000,000	46,600,000	19,000,000
Cash paid for income taxes	1,657,000	629,000	1,056,000
Operating loss carryforwards	6,700,000
Net deferred tax asset related to tax credit carryforwards	30,200,000
Net deferred tax asset related to credits	29,700,000
Operating Loss Carryforwards, Valuation Allowance	$ 3,600,000
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Expiration years of net operating loss carryforwards	Jan. 01, 2027
Tax Credit Carryforward, Expiration Date	Jan. 01, 2017
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Expiration years of net operating loss carryforwards	Jan. 01, 2033
Tax Credit Carryforward, Expiration Date	Jan. 01, 2032