Condensed Consolidating Statement Of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Condensed Statement of Income Captions [Line Items]
Net income	$ 35,813	$ 35,400	$ 57,407	$ 58,510
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	216	216	431	431
Foreign currency translation adjustment	175	509	(1,272)	1,030
Other comprehensive income (loss), net of tax	391	725	(841)	1,461
Comprehensive income	36,204	36,125	56,566	59,971
Parent [Member]
Condensed Statement of Income Captions [Line Items]
Net income	35,813	35,400	57,407	58,510
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	216	216	431	431
Foreign currency translation adjustment	175	509	(1,272)	1,030
Other comprehensive income (loss), net of tax	391	725	(841)	1,461
Comprehensive income	36,204	36,125	56,566	59,971
Guarantor Subsidiaries [Member]
Condensed Statement of Income Captions [Line Items]
Net income	4,124	3,685	6,462	7,288
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	4,124	3,685	6,462	7,288
Non-Guarantor Subsidiaries [Member]
Condensed Statement of Income Captions [Line Items]
Net income	6,169	9,514	15,025	16,776
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	0	0	0	0
Foreign currency translation adjustment	175	509	(1,272)	1,030
Other comprehensive income (loss), net of tax	175	509	(1,272)	1,030
Comprehensive income	6,344	10,023	13,753	17,806
Eliminations [Member]
Condensed Statement of Income Captions [Line Items]
Net income	(10,293)	(13,199)	(21,487)	(24,064)
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	0	0	0	0
Foreign currency translation adjustment	(175)	(509)	1,272	(1,030)
Other comprehensive income (loss), net of tax	(175)	(509)	1,272	(1,030)
Comprehensive income	(10,468)	(13,708)	(20,215)	(25,094)
Consolidated [Member]
Condensed Statement of Income Captions [Line Items]
Net income	35,813	35,400	57,407	58,510
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge	216	216	431	431
Foreign currency translation adjustment	175	509	(1,272)	1,030
Other comprehensive income (loss), net of tax	391	725	(841)	1,461
Comprehensive income	$ 36,204	$ 36,125	$ 56,566	$ 59,971