Business Combinations (Acquisition Date Fair Values Of Total Consideration Transferred) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Jan. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Business Combinations [Abstract]
Cash consideration, net of cash acquired	$ 108,247	[1]	$ 2,800	$ 11,375	[1]	$ 5,077	[1]
Contingent consideration	21,595			4,195		6,070
Deferred acquisition obligations	24,213			3,438		563
Total consideration transferred	$ 154,055			$ 19,008		$ 11,710

[1] Included in 2011 is $2.8 million related to an acquisition closed in December 2010 and paid in January 2011.