Income Taxes - Narrative (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Income Tax Disclosure [Abstract]      
Effective income tax rate (percent) 38.40% 38.20%  
Gross unrecognized tax benefit $ 3.2   $ 3.4
Expected change in unrecognized tax benefits 0.1    
Accrued interest on income taxes 4.0   3.9
Accrued penalties on income taxes $ 0.1   $ 0.1