Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Taxes
Effective tax rate (as a percent)	44.20%	2.30%
Discrete tax expense relating to a change in state apportionment (as a percent)	4.40%
Effective tax rate before discrete tax expense relating to a change in state apportionment (as a percent)	39.80%
Federal income tax	$ 0
State income tax	0
Unrecognized tax benefits, uncertain tax positions taken in prior years	0	6
Unrecognized tax benefits, interest and penalties accrued	$ 9