Fair Values of Financial Instruments Schedule of Fair Values of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Assets
Cash and cash equivalents	$ 103,662	$ 136,411	$ 102,800	$ 133,086
Cash and cash equivalents, at fair value	103,662	136,411
Foreign Exchange Forwards	122	146
Liabilities
Interest Rate Swaps	1,482	2,725
Foreign Exchange Forwards Liability	108	114
USD Denominated Term Loan [Member]
Liabilities
Term loans	270,000	277,500
Term loans, at fair value	268,219	275,365
Line of Credit [Member]
Liabilities
Multicurrency revolving line of credit	140,000	140,000
Line of Credit Facility, Fair Value of Amount Outstanding	138,930	138,751
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Foreign exchange forwards, asset, at fair value	122	146
Liabilities
Interest rate swap contracts	1,482	2,725
Foreign exchange forwards, liability, at fair value	$ 108	$ 114