Summary of Significant Accounting Policies (Details 6) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Aggregate amortization expense
Aggregate amortization expense	$ 13,391	$ 9,380	$ 7,790
Estimated amortization expense related to intangible assets
2012	17,470
2013	15,207
2014	12,903
2015	11,048
2016	7,820
Thereafter	27,955
Total	$ 92,403

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Aggregate amount of intangible asset amortization recognized as expense during the period.

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The aggregate estimated amortization expense for succeeding fiscal years for intangible assets subject to amortization.

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The amount of amortization expense expected to be recognized for the remainder of the finite-lived intangible asset useful life after the fifth succeeding fiscal year.

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The amount of amortization expense expected to be recognized during year two of the five succeeding fiscal years.

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