Fair Values of Financial Instruments Schedule of Fair Values of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assets
Cash and cash equivalents	$ 136,411	$ 133,086	$ 169,477	$ 121,893
Cash and cash equivalents, at fair value	136,411	133,086
Foreign exchange forwards, asset	146	241
Liabilities
Interest rate swaps	2,725	0
Foreign exchange forwards, liability	114	222
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Foreign exchange forwards, asset, at fair value	146	241
Liabilities
Interest rate swaps, at fair value	2,725	0
Foreign exchange forwards, liability, at fair value	114	222
2011 Senior Secured Credit Facility [Member]
Liabilities
Multicurrency revolving line of credit	140,000	160,000
Multicurrency revolving line of credit, Fair Value of Amount Outstanding	138,751	163,269
2011 Senior Secured Credit Facility [Member] | USD Denominated Term Loan [Member]
Liabilities
Term loans	277,500	292,502
Term loans, at fair value	$ 275,365	$ 296,856