Fair Values of Financial Instruments Schedule of Fair Values of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Assets
Cash and cash equivalents	$ 154,438	$ 133,086	$ 133,412	$ 169,477
Cash and cash equivalents, at fair value	154,438	133,086
Foreign exchange forwards, asset	54	241
Liabilities
Foreign exchange forwards, liability	91	222
2011 Senior Secured Credit Facility [Member] | USD Denominated Term Loan [Member]
Liabilities
Term loans	288,752	292,502
Term loans, at fair value	292,894	296,856
2011 Senior Secured Credit Facility [Member] | Line of Credit [Member]
Liabilities
Line of Credit Facility, Amount Outstanding	150,000	160,000
Line of Credit Facility, Fair Value of Amount Outstanding	152,975	163,269
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Foreign exchange forwards, asset, at fair value	54	241
Liabilities
Foreign exchange forwards, liability, at fair value	$ 91	$ 222