Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Taxes
Effective income tax rates (as a percent)	41.70%	39.50%	39.10%	38.80%
Uncertain tax positions	$ 0		$ 0