Stock-Based Compensation (Stock-Based Compensation Expense Included In Consolidated Statements Of Operations) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	$ 9,028	$ 6,745	$ 4,673
Income tax benefit	(2,854)	(2,185)	(1,688)
Cost Of Services [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	2,737	1,825	1,096
Operating Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	$ 6,291	$ 4,920	$ 3,577