Acquisitions (Schedule Of Pro Forma Financial Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Allstar Business Solutions Limited [Member]	Dec. 31, 2010 Allstar Business Solutions Limited [Member]	Dec. 31, 2010 CLC Group Inc And Subsidiaries [Member]	Dec. 31, 2009 CLC Group Inc And Subsidiaries [Member]
Business Acquisition [Line Items]
Revenues, net	$ 595,864	$ 505,287	$ 433,841	$ 370,381
Income before income taxes	223,251	162,153	151,280	137,092
Net income	$ 156,430	$ 115,496	$ 107,896	$ 93,413
Earnings per share, Basic	$ 1.94	$ 3.22	$ 3.00	$ 2.33
Earnings per share, Diluted	$ 1.87	$ 1.43	$ 1.34	$ 1.15
Weighted average shares outstanding, Basic	80,610	35,434	35,434	33,802
Weighted average shares outstanding, Diluted	83,654	80,751	80,751	80,979