Summary of Significant Accounting Policies (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Amortizable intangible assets
Gross carrying amount	$ 674,403
Accumulated amortization	(221,960)
Net carrying amount	452,443
Amortization expense associated with amortizable intangible assets (including deferred financing costs)	9,601	8,251
Customer Relationships and Acquisition Costs.
Amortizable intangible assets
Gross carrying amount	612,560
Accumulated amortization	(196,242)
Net carrying amount	416,318
Core Technology.
Amortizable intangible assets
Gross carrying amount	3,760
Accumulated amortization	(2,583)
Net carrying amount	1,177
Trademarks and Non-Compete Agreements
Amortizable intangible assets
Gross carrying amount	3,075
Accumulated amortization	(2,562)
Net carrying amount	513
Deferred Financing Costs
Amortizable intangible assets
Gross carrying amount	55,008
Accumulated amortization	(20,573)
Net carrying amount	$ 34,435