Fair Values of Financial Instruments Schedule of Fair Values of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assets
Cash and cash equivalents	$ 124,805	$ 136,411	$ 133,086	$ 169,477
Reported Value Measurement [Member]
Assets
Foreign exchange forward contracts	41	146
Cash and cash equivalents	124,805	136,411
Liabilities
Interest rate swaps, at fair value	2,031	2,725
Foreign exchange forwards, liability, at fair value	145	114
Reported Value Measurement [Member] | Line of Credit [Member]
Liabilities
Multicurrency revolving line of credit	120,000	140,000
Reported Value Measurement [Member] | USD Denominated Term Loan [Member]
Liabilities
Term loans	258,750	277,500
Estimate of Fair Value Measurement [Member]
Assets
Foreign exchange forward contracts	41	146
Cash and cash equivalents, at fair value	124,805	136,411
Liabilities
Interest rate swaps, at fair value	2,031	2,725
Foreign exchange forwards, liability, at fair value	145	114
Estimate of Fair Value Measurement [Member] | Line of Credit [Member]
Liabilities
Multicurrency revolving line of credit, Fair Value of Amount Outstanding	119,609	138,751
Estimate of Fair Value Measurement [Member] | USD Denominated Term Loan [Member]
Liabilities
Term loans, at fair value	$ 258,011	$ 275,365