Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Taxes
Income tax expense	$ 2,644	$ 5,149	$ 10,810	$ 13,864
Effective income tax rate (as a percent)	37.30%	36.70%	37.90%	37.30%
Federal statutory rate (as a percent)			35.00%	35.00%