Guarantor Subsidiaries (Consolidating Statement of Changes In Equity) (Details) - USD ($) $ in Thousands	3 Months Ended					6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 746,800	$ 803,000	$ 797,800	$ 807,300		$ 803,000	$ 807,300
Issuance of treasury stock		(500)	0	0
Purchase of treasury stock	0	(140,600)	(16,800)	(13,300)
Amounts related to share-based compensation	0	(5,600)	(200)	(4,100)
Share-based compensation expense	2,800	2,800	2,800	2,600
Net income	168,900	89,300	32,700	5,300		258,200	38,000
Ending balance	918,000	746,800	816,300	797,800		918,000	816,300
Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		1,100				1,100
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	500	500	500	500		500	500
Issuance of common stock	0	0	0	0
Ending balance	500	500	500	500		500	500
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,235,200)	(1,099,800)	(948,000)	(940,300)		(1,099,800)	(940,300)
Issuance of treasury stock	0	5,200	100	5,600
Purchase of treasury stock	0	(140,600)	(16,800)	(13,300)
Ending balance	(1,235,200)	(1,235,200)	(964,700)	(948,000)		(1,235,200)	(964,700)
APIC
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	530,200	538,700	531,900	539,000		538,700	539,000
Issuance of treasury stock		(5,700)	(100)	(5,600)
Amounts related to share-based compensation	0	(5,600)	(200)	(4,100)
Share-based compensation expense	2,800	2,800	2,800	2,600
Ending balance	533,000	530,200	534,400	531,900		533,000	534,400
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,453,300	1,362,900	1,213,400	1,208,100		1,362,900	1,208,100
Net income	168,900	89,300	32,700	5,300
Ending balance	1,622,200	1,453,300	1,246,100	1,213,400		1,622,200	1,246,100
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		1,100				1,100
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(2,000)	700	0	0		700	0
Other comprehensive income (loss)		(2,700)	0	0
Net income	(500)
Ending balance	(2,500)	(2,000)	0	0		(2,500)	0
Eliminations
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		(2,735,700)				(2,735,700)
Net income	(168,700)		(32,600)			(257,900)	(37,700)
Ending balance	(2,993,600)					(2,993,600)
Eliminations | Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(100)	(100)	(100)	(100)		(100)	(100)
Ending balance	(100)	(100)	(100)	(100)		(100)	(100)
Eliminations | Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	0	0	0	0		0	0
Eliminations | APIC
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,368,400)	(1,368,400)	(1,368,400)	(1,368,400)		(1,368,400)	(1,368,400)
Ending balance	(1,368,400)	(1,368,400)	(1,368,400)	(1,368,400)		(1,368,400)	(1,368,400)
Eliminations | Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,456,400)	(1,367,200)	(1,218,000)	(1,212,900)		(1,367,200)	(1,212,900)
Net income	(168,700)	(89,200)	(32,600)	(5,100)
Ending balance	(1,625,100)	(1,456,400)	(1,250,600)	(1,218,000)		(1,625,100)	(1,250,600)
Eliminations | AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	0	0	0	0		0	0
Parent Company | Reportable Legal Entities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		2,591,900				2,591,900
Net income	168,900		32,700			258,200	38,000
Ending balance	2,709,000					2,709,000
Parent Company | Reportable Legal Entities | Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	500	500	500	500		500	500
Ending balance	500	500	500	500		500	500
Parent Company | Reportable Legal Entities | Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,235,200)	(1,099,800)	(948,000)	(940,300)		(1,099,800)	(940,300)
Issuance of treasury stock	0	5,200	100	5,600
Purchase of treasury stock	0	(140,600)	(16,800)	(13,300)
Ending balance	(1,235,200)	(1,235,200)	(964,700)	(948,000)		(1,235,200)	(964,700)
Parent Company | Reportable Legal Entities | APIC
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,183,100	1,188,800	1,189,500	1,195,100		1,188,800	1,195,100
Issuance of treasury stock		(5,700)	(100)	(5,600)
Ending balance	1,183,100	1,183,100	1,189,400	1,189,500		1,183,100	1,189,400
Parent Company | Reportable Legal Entities | Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	2,591,700	2,502,400	2,187,100	2,181,800		2,502,400	2,181,800
Net income	168,900	89,300	32,700	5,300
Ending balance	2,760,600	2,591,700	2,219,800	2,187,100		2,760,600	2,219,800
Parent Company | Reportable Legal Entities | AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	0	0	0	0		0	0
Issuer | Reportable Legal Entities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		741,400				741,400
Net income	168,900		32,700			258,200	38,000
Ending balance	997,500					997,500
Issuer | Reportable Legal Entities | Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	0	0	0	0		0	0
Issuer | Reportable Legal Entities | Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	0	0	0	0		0	0
Issuer | Reportable Legal Entities | APIC
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	576,000	578,800	571,300	572,800		578,800	572,800
Amounts related to share-based compensation		(5,600)	(200)	(4,100)
Share-based compensation expense	2,800	2,800	2,800	2,600
Ending balance	578,800	576,000	573,900	571,300		578,800	573,900
Issuer | Reportable Legal Entities | Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	252,300	161,900	178,200	172,900		161,900	172,900
Net income	168,900	89,300	32,700	5,300
Ending balance	421,200	252,300	210,900	178,200		421,200	210,900
Issuer | Reportable Legal Entities | Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		1,100				1,100
Issuer | Reportable Legal Entities | AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(2,000)	700	0	0		700	0
Other comprehensive income (loss)		(2,700)
Net income	(500)
Ending balance	(2,500)	(2,000)	0	0		(2,500)	0
Guarantor Subsidiaries | Reportable Legal Entities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		51,100				51,100
Net income	(200)		(100)			(300)	(300)
Ending balance	50,800					50,800
Guarantor Subsidiaries | Reportable Legal Entities | Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	100	100	100	100		100	100
Ending balance	100	100	100	100		100	100
Guarantor Subsidiaries | Reportable Legal Entities | Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	0	0	0	0		0	0
Guarantor Subsidiaries | Reportable Legal Entities | APIC
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	52,000	52,000	52,000	52,000		52,000	52,000
Ending balance	52,000	52,000	52,000	52,000		52,000	52,000
Guarantor Subsidiaries | Reportable Legal Entities | Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,100)	(1,000)	(700)	(500)		(1,000)	(500)
Net income	(200)	(100)	(100)	(200)
Ending balance	(1,300)	(1,100)	(800)	(700)		(1,300)	(800)
Guarantor Subsidiaries | Reportable Legal Entities | AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	0	0	0	0		0	0
Non-Guarantor Subsidiaries | Reportable Legal Entities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		154,300				154,300
Net income	0		0			0	0
Ending balance	154,300					154,300
Non-Guarantor Subsidiaries | Reportable Legal Entities | Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	0	0	0	0		0	0
Non-Guarantor Subsidiaries | Reportable Legal Entities | Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	0	0	0	0		0	0
Non-Guarantor Subsidiaries | Reportable Legal Entities | APIC
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	87,500	87,500	87,500	87,500		87,500	87,500
Ending balance	87,500	87,500	87,500	87,500		87,500	87,500
Non-Guarantor Subsidiaries | Reportable Legal Entities | Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	66,800	66,800	66,800	66,800		66,800	66,800
Net income				0	$ 0
Ending balance	66,800	66,800	66,800	66,800		66,800	66,800
Non-Guarantor Subsidiaries | Reportable Legal Entities | AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0	0	0	0		0	0
Ending balance	$ 0	$ 0	$ 0	$ 0		$ 0	$ 0