Fair Value of Assets and Liabilities (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Fair value assets measured on recurring basis
Assets held in a rabbi trust	$ 8,400	$ 8,163
Contingent consideration on sale of business	0	2,030
Total	271,170	284,241
Fair value liabilities measured on recurring basis
Deferred compensation	8,400	8,163
Total	13,082	15,594
Level 1 [Member] | Foreign exchange forward contracts [Member]
Fair value assets measured on recurring basis
Foreign exchange forward contracts	0	0
Level 2 [Member] | Foreign exchange forward contracts [Member]
Fair value assets measured on recurring basis
Foreign exchange forward contracts	1,541	925
Level 3 [Member] | Foreign exchange forward contracts [Member]
Fair value assets measured on recurring basis
Foreign exchange forward contracts	0	0
Level 1 [Member] | Foreign exchange forward contracts [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	0	0
Level 2 [Member] | Foreign exchange forward contracts [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	1,241	4,060
Level 3 [Member] | Foreign exchange forward contracts [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	0	0
Foreign exchange forward contracts [Member]
Fair value assets measured on recurring basis
Foreign exchange forward contracts	1,541	925
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	1,241	4,060
Certificates Of Deposit [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	229,532	221,706
Certificates Of Deposit [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	229,532	221,706
Certificates Of Deposit [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	0	0
Certificates Of Deposit [Member] | Level 3 [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	0	0
Level 1 [Member] | Interest Rate Swap [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	0	0
Level 2 [Member] | Interest Rate Swap [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	3,441	3,371
Level 3 [Member] | Interest Rate Swap [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	0	0
Interest Rate Swap [Member]
Fair value liabilities measured on recurring basis
Fair value Liabilities measured on recurring basis- Derivatives	3,441	3,371
U.S. dollar indexed bond funds [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	31,697	51,417
U.S. dollar indexed bond funds [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] | Level 2 [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	31,697	51,417
U.S. dollar indexed bond funds [Member] | Level 3 [Member]
Fair value assets measured on recurring basis
Fair value measured on recurring basis, investments	0	0
Level 1 [Member]
Fair value assets measured on recurring basis
Assets held in a rabbi trust	8,400	8,163
Contingent consideration on sale of business	0	0
Total	237,932	229,869
Level 1 [Member]
Fair value liabilities measured on recurring basis
Deferred compensation	8,400	8,163
Total	8,400	8,163
Level 2 [Member]
Fair value assets measured on recurring basis
Assets held in a rabbi trust	0	0
Contingent consideration on sale of business	0	0
Total	33,238	52,342
Level 2 [Member]
Fair value liabilities measured on recurring basis
Deferred compensation	0	0
Total	4,682	7,431
Level 3 [Member]
Fair value assets measured on recurring basis
Assets held in a rabbi trust	0	0
Contingent consideration on sale of business	0	2,030
Total	0	2,030
Level 3 [Member]
Fair value liabilities measured on recurring basis
Deferred compensation	0	0
Total	$ 0	$ 0