Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Summary of accounts Receivable
Total receivables	$ 157,497		$ 130,592
Less allowance for doubtful accounts	(4,158)		(4,028)
Accounts receivable, net	153,339	[1]	126,564	[1]
Billed receivables [Member]
Summary of accounts Receivable
Total receivables	148,055		122,874
Unbilled receivables [Member]
Summary of accounts Receivable
Total receivables	$ 9,442		$ 7,718

[1] See Note 19. Related Parties for further information.