Fair Value of Assets and Liabilities - Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Total	$ 254,747	$ 269,629
Fair value liabilities measured on recurring basis
Total	13,092	11,254
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Total	225,387	265,301
Fair value liabilities measured on recurring basis
Total	10,377	6,783
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Total	29,360	4,328
Fair value liabilities measured on recurring basis
Total	2,715	4,471
Foreign exchange forward contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Foreign exchange forward contracts	1,382	960
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	364	913
Foreign exchange forward contracts [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Foreign exchange forward contracts	0	0
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	0	0
Foreign exchange forward contracts [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Foreign exchange forward contracts	1,382	960
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	364	913
Interest rate swap [Member] | Fair Value, Measurements, Recurring [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	2,351	3,558
Interest rate swap [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	0	0
Interest rate swap [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	2,351	3,558
Certificates of deposit [Member] | Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	215,010	258,518
Certificates of deposit [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	215,010	258,518
Certificates of deposit [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	0	0
U.S. dollar indexed bond funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	27,978	3,368
U.S. dollar indexed bond funds [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	0	0
U.S. dollar indexed bond funds [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	27,978	3,368
Assets held in rabbi trusts [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	10,377	6,783
Assets held in rabbi trusts [Member] | Fair Value, Measurements, Recurring [Member]
Fair value assets measured on recurring basis
Assets held in rabbi trusts	10,377	6,783
Fair value liabilities measured on recurring basis
Deferred compensation	10,377	6,783
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	10,377	6,783
Fair value liabilities measured on recurring basis
Deferred compensation	10,377	6,783
Assets held in rabbi trusts [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Assets held in rabbi trusts	0	0
Fair value liabilities measured on recurring basis
Deferred compensation	$ 0	$ 0