Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 46,514		$ 41,484	$ 83,189		$ 75,705
Other comprehensive loss, net of tax:
Interest rate swap (cash flow hedge) – gain (loss)	814	[1]	(433)	1,375	[1]	(401)
Defined benefit pension plans – actuarial gain (loss)	1	[1]	(52)	24	[1]	(106)
Foreign currency translation adjustments	(1,220)	[1]	(4,339)	(5,009)	[1]	(1,663)
Other comprehensive loss	(405)	[1]	(4,824)	(3,610)	[1]	(2,170)
Comprehensive income	$ 46,109		$ 36,660	$ 79,579		$ 73,535

[1] Amounts in parentheses represent debits.