Fair Value of Assets and Liabilities - Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Total	$ 148,613	$ 254,747
Fair value liabilities measured on recurring basis
Total	11,320	13,092
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Total	143,462	225,387
Fair value liabilities measured on recurring basis
Total	9,662	10,377
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Total	5,151	29,360
Fair value liabilities measured on recurring basis
Total	1,658	2,715
Foreign exchange forward contracts | Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Foreign exchange forward contracts	5,151	1,382
Fair value liabilities measured on recurring basis
Derivative Liability	180	364
Foreign exchange forward contracts | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Foreign exchange forward contracts	5,151	1,382
Fair value liabilities measured on recurring basis
Derivative Liability	180	364
Interest rate swaps | Fair Value, Measurements, Recurring [Member]
Fair value liabilities measured on recurring basis
Derivative Liability	1,478	2,351
Interest rate swaps | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value liabilities measured on recurring basis
Derivative Liability	1,478	2,351
Certificates of deposit | Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Investments, Fair Value Disclosure	133,800	215,010
Certificates of deposit | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Investments, Fair Value Disclosure	133,800	215,010
U.S. dollar indexed bond funds | Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Investments, Fair Value Disclosure	0	27,978
U.S. dollar indexed bond funds | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Investments, Fair Value Disclosure	0	27,978
Assets held in rabbi trusts [Member]
Fair value assets measured on recurring basis
Assets held in rabbi trusts	9,662	10,377
Assets held in rabbi trusts [Member] | Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Assets held in rabbi trusts	9,662	10,377
Fair value liabilities measured on recurring basis
Deferred compensation	9,662	10,377
Assets held in rabbi trusts [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Assets held in rabbi trusts	9,662	10,377
Fair value liabilities measured on recurring basis
Deferred compensation	$ 9,662	$ 10,377