Income Taxes (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Taxes
Effective tax rate (as a percent)	32.10%	25.70%	32.10%	32.50%
Income tax at U.S. federal statutory tax rate (as a percent)			35.00%