Condensed Consolidating Financial Statements Condensed Consolidating Statement Of Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Condensed Consolidating Financial Statements [Line Items]
Net income	$ 39,365	$ 38,716	$ 97,875	$ 90,266
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	215	215	646	646
Foreign currency translation adjustment	(1,387)	524	(357)	(1,803)
Other comprehensive income (loss), net of tax	(1,172)	739	289	(1,157)
Comprehensive income	38,193	39,455	98,164	89,109
Parent [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	39,365	38,716	97,875	90,266
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	215	215	646	646
Foreign currency translation adjustment	(1,387)	524	(357)	(1,803)
Other comprehensive income (loss), net of tax	(1,172)	739	289	(1,157)
Comprehensive income	38,193	39,455	98,164	89,109
Guarantor Subsidiaries [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	1,919	3,172	9,207	9,236
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	0	0	0	0
Foreign currency translation adjustment	0	0	0	0
Other comprehensive income (loss), net of tax	0	0	0	0
Comprehensive income	1,919	3,172	9,207	9,236
Non-Guarantor Subsidiaries [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	8,287	9,859	25,063	25,455
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	0	0	0	0
Foreign currency translation adjustment	(1,387)	524	(357)	(1,803)
Other comprehensive income (loss), net of tax	(1,387)	524	(357)	(1,803)
Comprehensive income	6,900	10,383	24,706	23,652
Eliminations [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	(10,206)	(13,031)	(34,270)	(34,691)
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	0	0	0	0
Foreign currency translation adjustment	1,387	(524)	357	1,803
Other comprehensive income (loss), net of tax	1,387	(524)	357	1,803
Comprehensive income	(8,819)	(13,555)	(33,913)	(32,888)
Consolidated [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	39,365	38,716	97,875	90,266
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	215	215	646	646
Foreign currency translation adjustment	(1,387)	524	(357)	(1,803)
Other comprehensive income (loss), net of tax	(1,172)	739	289	(1,157)
Comprehensive income	$ 38,193	$ 39,455	$ 98,164	$ 89,109