Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 38,194		$ 31,375	$ 121,383		$ 107,080
Other comprehensive income, net of tax:
Interest rate swap (cash flow hedge) – gain (loss)	261	[1]	(282)	1,636	[1]	(683)
Defined benefit pension plans – actuarial gain (loss)	6	[1]	(51)	30	[1]	(157)
Foreign currency translation adjustments	4,109	[1]	5,383	(900)	[1]	3,720
Other comprehensive income	4,376	[1]	5,050	766	[1]	2,880
Comprehensive income	$ 42,570		$ 36,425	$ 122,149		$ 109,960

[1] Amounts in parentheses represent debits (deferred losses).