Accrued Expenses (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Accrued Expenses
Defined contribution plan	$ 782	$ 1,088
Accrued payroll and related benefits	3,053	3,024
Sales and use tax	1,272	1,367
Bonus accrual	582	4,845
Interest payable	2,192	345
Unrealized loss on derivatives	6,641	265
Other accrued expenses	980	1,964
Total accrued expenses	$ 15,502	$ 12,898