Condensed Consolidating Financial Statements Condensed Consolidating Statement Of Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income	$ 15,523	$ 19,997
Amortization of loss on cash flow hedge	215	215
Foreign currency translation adjustment, net	(232)	412
Actuarial loss	0	20
Other comprehensive income (loss), net of tax	(17)	647
Comprehensive income	15,506	20,644
Parent [Member]
Net income	15,523	19,997
Amortization of loss on cash flow hedge	215	215
Foreign currency translation adjustment, net	(232)	412
Actuarial loss		20
Other comprehensive income (loss), net of tax	(17)	647
Comprehensive income	15,506	20,644
Guarantor Subsidiaries [Member]
Net income	2,369	4,301
Amortization of loss on cash flow hedge	0	0
Foreign currency translation adjustment, net	0	6
Actuarial loss		20
Other comprehensive income (loss), net of tax	0	26
Comprehensive income	2,369	4,327
Non-Guarantor Subsidiaries [Member]
Net income	5,598	2,580
Amortization of loss on cash flow hedge	0	0
Foreign currency translation adjustment, net	(232)	391
Actuarial loss		0
Other comprehensive income (loss), net of tax	(232)	391
Comprehensive income	5,366	2,971
Eliminations [Member]
Net income	(7,967)	(6,881)
Amortization of loss on cash flow hedge	0	0
Foreign currency translation adjustment, net	232	(397)
Actuarial loss		(20)
Other comprehensive income (loss), net of tax	232	(417)
Comprehensive income	(7,735)	(7,298)
Consolidated [Member]
Net income	15,523	19,997
Amortization of loss on cash flow hedge	215	215
Foreign currency translation adjustment, net	(232)	412
Actuarial loss		20
Other comprehensive income (loss), net of tax	(17)	647
Comprehensive income	$ 15,506	$ 20,644