Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accrued Liabilities
Compensation and benefits	$ 45,418	$ 39,766
Customer advances	1,077	1,024
Deferred revenue	18,916	18,227
Taxes, other than income	9,749	6,982
Liabilities assumed in business combinations	6,122	1,450
Accrued contract costs	11,461	19,941
Accrued interest	8,694	9,668
Other	43,234	39,867
Total Accrued Liabilities	$ 144,671	$ 136,925