Summary Of Operations And Significant Accounting Policies (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				3 Months Ended				3 Months Ended		3 Months Ended		3 Months Ended
	Mar. 31, 2013 segment	Mar. 31, 2012	Mar. 31, 2013 Minimum	Mar. 31, 2013 Maximum	Mar. 31, 2013 Two Thousand Employee Stock Purchase Plan	Mar. 31, 2000 Two Thousand Employee Stock Purchase Plan	Mar. 31, 2013 Employee Stock Purchase Plan, 2010	Jun. 30, 2010 Employee Stock Purchase Plan, 2010	Mar. 31, 2013 Incentive Stock Option	Mar. 31, 2013 Incentive Stock Option Nineteen Ninety Eight Plan Maximum	Mar. 31, 2013 Incentive Stock Option Two Thousand Plan	Mar. 31, 2013 Incentive Stock Option Nineteen Ninety Eight and Two Thousand Plan	Mar. 31, 2013 Incentive Stock Option Two Thousand Nine Plan	Mar. 31, 2013 Incentive Stock Option Two Thousand Nine Plan 2009 Plan
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Typical service agreements	12 months
Typical service agreements termination notice period			30 days	90 days
Fees and related labor costs, recognition period (current estimate of term of customer relationship)	48 months
Weighted average fair value of stock options granted	$ 6.68	$ 6.55
Shares of common stock available for issuance						450,000	818,000	1,000,000	23,817,744	5,850,000		10,000,000	15,300,000
Increase in number of shares of common stock available for issuance											4,150,000		6,000,000	4,250,000
Stock option term	10 years
Unrecognized compensation cost related to nonvested share-based compensation arrangements									$ 37,282
Weighted average recognition period of unrecognized compensation cost									2 years
Shares of common stock available for issuance, expiration date					Apr. 01, 2010
Total value of stock options exercised	778
Total intrinsic value of options exercisable	24,070
Total intrinsic value of nonvested options	8,902
Total intrinsic value of all outstanding options	32,972
Effect of option to purchase share of common stock on diluted net income per share	3,626,240	4,509,618
Weighted average exercise price of options		$ 5.37
Number of operating segments	2
Aggregate amortization expense for intangible assets	418	77
Estimated amortization expense in 2013	3,263
Estimated amortization expense in 2014	4,134
Estimated amortization expense in 2015	3,772
Estimated amortization expense in 2016	3,313
Estimated amortization expense in 2017	718
Estimated amortization expenses thereafter 2017	$ 113