Condensed Consolidating Financial Statements Condensed Consolidating Statement Of Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Condensed Consolidating Financial Statements [Line Items]
Net income	$ 35,400	$ 31,807	$ 58,510	$ 51,550
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	216	216	431	431
Foreign currency translation adjustment	509	(2,082)	1,030	(2,327)
Other comprehensive income (loss), net of tax	725	(1,866)	1,461	(1,896)
Comprehensive income	36,125	29,941	59,971	49,654
Parent [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	35,400	31,807	58,510	51,550
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	216	216	431	431
Foreign currency translation adjustment	509	(2,082)	1,030	(2,327)
Other comprehensive income (loss), net of tax	725	(1,866)	1,461	(1,896)
Comprehensive income	36,125	29,941	59,971	49,654
Guarantor Subsidiaries [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	3,685	3,406	7,288	6,064
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	3,685	3,406	7,288	6,064
Non-Guarantor Subsidiaries [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	9,514	9,809	16,776	15,596
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	0	0	0	0
Foreign currency translation adjustment	509	(2,082)	1,030	(2,327)
Other comprehensive income (loss), net of tax	509	(2,082)	1,030	(2,327)
Comprehensive income	10,023	7,727	17,806	13,269
Eliminations [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	(13,199)	(13,215)	(24,064)	(21,660)
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	0	0	0	0
Foreign currency translation adjustment	(509)	2,082	(1,030)	2,327
Other comprehensive income (loss), net of tax	(509)	2,082	(1,030)	2,327
Comprehensive income	(13,708)	(11,133)	(25,094)	(19,333)
Consolidated [Member]
Condensed Consolidating Financial Statements [Line Items]
Net income	35,400	31,807	58,510	51,550
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	216	216	431	431
Foreign currency translation adjustment	509	(2,082)	1,030	(2,327)
Other comprehensive income (loss), net of tax	725	(1,866)	1,461	(1,896)
Comprehensive income	$ 36,125	$ 29,941	$ 59,971	$ 49,654