Accrued Expenses (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accrued Expenses
Accrued compensation and benefits	$ 4,836	$ 5,770
Accrued taxes	4,484	5,293
Accrued interest	8,319	3,230
Accrued commissions	1,091	1,229
Other accrued expenses	4,797	4,793
Accrued liabilities	$ 23,527	$ 20,315