Fixed Assets (Schedule Of Fixed Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010 years
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 207,796	$ 165,114
Less: accumulated depreciation and amortization	(85,233)	(50,820)
Fixed assets, net	122,563	114,294
Computer Equipment And Software [Member]
Property, Plant and Equipment [Line Items]
Fixed assets, gross	157,845	120,111
Estimated Useful Life, Minimum (in years)	3	3
Estimated Useful Life, Maximum (in years)	5	5
Furniture And Fixtures [Member]
Property, Plant and Equipment [Line Items]
Fixed assets, gross	18,128	15,696
Estimated Useful Life, Minimum (in years)	5	5
Estimated Useful Life, Maximum (in years)	7	7
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Fixed assets, gross	22,243	21,079
Estimated Useful Life, Minimum (in years)	7	7
Estimated Useful Life, Maximum (in years)	8	8
Assets Under Capital Lease [Member]
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 9,580	$ 8,228
Estimated Useful Life, Average (in years)	3	3