Summary of Significant Accounting Policies (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Amortizable intangible assets
Gross carrying amount	$ 757,129
Accumulated amortization	(265,951)
Net carrying amount	491,178
Amortization expense associated with amortizable intangible assets (including deferred financing costs)	12,016	9,601
Customer Relationships and Acquisition Costs.
Amortizable intangible assets
Gross carrying amount	684,473
Accumulated amortization	(238,184)
Net carrying amount	446,289
Core Technology.
Amortizable intangible assets
Gross carrying amount	3,676
Accumulated amortization	(3,133)
Net carrying amount	543
Trademarks and Non-Compete Agreements
Amortizable intangible assets
Gross carrying amount	4,942
Accumulated amortization	(3,084)
Net carrying amount	1,858
Deferred Financing Costs
Amortizable intangible assets
Gross carrying amount	64,038
Accumulated amortization	(21,550)
Net carrying amount	$ 42,488