Accounts Payable and Accrued Expenses (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Trade accounts payable	$ 11,061	$ 10,481
Accrued salaries, vacation and benefits	16,463	14,517
Other accrued expenses	17,393	13,075
Accrued contingent consideration	2,540	2,539
Negative cash book balance	0	1,888
Accounts payable and accrued expenses	$ 47,457	$ 42,500