Consolidated Statements of Changes in Shareholders Equity - USD ($)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Stockholders' Equity, Total [Member]	Treasury Stock, Common [Member]
Treasury Stock, Value	$ 1,078,800,000
Balance, shares at Dec. 31, 2016		121,642,556
Balance at Dec. 31, 2016		$ 1,200,000	$ 1,078,900,000	$ (186,900,000)	$ 2,113,900,000	$ 1,928,300,000
Net income	354,900,000					354,900,000
Dividends, Common Stock, Cash	(46,400,000)
Employee equity awards, shares		667,845
Employee equity awards, value			22,100,000			22,100,000
Stock forfeitures, shares		92,482
Net shares settled		250,066
Payment, Tax Withholding, Share-based Payment Arrangement	(14,200,000)
Excess tax benefits from share-based payment arrangements							$ 100,000
SERP shares issued		11,369
Treasury Stock, Value, Acquired, Cost Method	(502,100,000)
Other Comprehensive Income	58,400,000			58,400,000		58,400,000
Balance, shares at Dec. 31, 2017		114,447,605
Balance at Dec. 31, 2017		$ 1,100,000	1,086,900,000	(128,500,000)	2,422,400,000	1,801,000,000.0	(100,000)
Treasury Stock, Carrying Basis	(7,531,617)
Treasury Stock, Value	1,580,900,000
Net income	617,000,000.0					617,000,000.0
Impact on Retained Earnings, Adoption of ASC 606	(277,000,000.0)
Dividends, Common Stock, Cash	(49,200,000)
Employee equity awards, shares		466,719
Employee equity awards, value			27,400,000			27,400,000
Stock forfeitures, shares		47,962
Net shares settled		177,812
Payment, Tax Withholding, Share-based Payment Arrangement	(15,600,000)
Excess tax benefits from share-based payment arrangements							100,000
SERP shares issued		24,996
Supplemental Retirement Plan Shares Issued Value	2,100,000		2,100,000
Treasury Stock, Value, Acquired, Cost Method	(800,100,000)
Stock Repurchased During Period, Value	(800,000,000.0)
Other Comprehensive Income	(68,100,000)			(68,100,000)		(68,100,000)
Balance, shares at Dec. 31, 2018		105,461,817
Balance at Dec. 31, 2018	1,237,600,000	$ 1,100,000	1,100,900,000	(196,600,000)	2,713,200,000	1,237,600,000	0
Treasury Stock, Carrying Basis	(9,251,729)
Treasury Stock, Value	(2,381,000,000.0)
Net income	530,100,000					530,100,000
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	8,300,000			(8,300,000)
Dividends, Common Stock, Cash	(50,300,000)
Employee equity awards, shares		448,594
Employee equity awards, value			34,400,000			34,400,000
Stock forfeitures, shares		125,055
Net shares settled		137,500
Payment, Tax Withholding, Share-based Payment Arrangement	$ (12,900,000)
Excess tax benefits from share-based payment arrangements							0
SERP shares issued	6,214	32,341
Supplemental Retirement Plan Shares Issued Value	$ 2,600,000		2,600,000
Treasury Stock, Value, Acquired, Cost Method	(75,800,000)
Stock Repurchased During Period, Value	(75,800,000)
Other Comprehensive Income	95,700,000			95,700,000		95,700,000
Balance, shares at Dec. 31, 2019		104,882,379
Balance at Dec. 31, 2019	1,761,400,000	$ 1,100,000	$ 1,125,000,000.0	$ (109,200,000)	$ 3,201,300,000	$ 1,761,400,000	$ 0
Treasury Stock, Carrying Basis	(804,032)
Treasury Stock, Value	$ (2,456,800,000)