Share-Based Compensation Plans (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) shares $ / shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares
Share-based employee compensation expense | $	$ 70.5	$ 80.2	$ 93.4
Unamortized share-based employee compensation, amortization period	5 years
Unamortized share-based employee compensation | $	$ 160.7
Excess tax benefit from share-based compensation | $	$ 7.4	$ 20.8
Option Activity [Roll Forward]
January 1	1,593,422	719,757	1,140,547
Granted	0	1,000,000	0
Exercised	(500,122)	(102,335)	(420,790)
Forfeited	(105,250)	(24,000)	0
December 31	988,050	1,593,422	719,757
Exercisable December 31	117,300	617,422	695,757
January 1, Weighted Average Exercise Price | $ / shares	$ 63.11	$ 27.88	$ 28.86
Granted, Weighted Average Exercise Price | $ / shares		84.94
Exercised, Weighted Average Exercise Price | $ / shares	24.43	23.40	30.56
Forfeited, Weighted Average Exercise Price | $ / shares	84.94	84.94
December 31, Weighted Average Exercise Price | $ / shares	80.37	63.11	27.88
Exercisable December 31, Weighted Average Exercise Price | $ / shares	$ 46.43	28.61	$ 26.54
Options Outstanding and Exercisable [Abstract]
Options Outstanding, Shares	988,050
Options Exercisable, Shares	117,300
Black-Scholes Assumptions and Weighted Average Fair Value Per Share for Options Granted [Abstract]
Weighted average fair value per option granted | $ / shares		$ 9.87
Expected life		4 years 6 months
Risk free interest rate		2.00%
Expected volatility		16.30%
Dividend yield		2.60%
Exercise Price Range - $23.00 to $24.00
Options Outstanding and Exercisable [Abstract]
Range of Exercise Prices, lower range limit | $ / shares	$ 23.00
Range of Exercise Prices, upper range limit | $ / shares	$ 24.00
Options Outstanding, Shares	57,300
Options Outstanding, Weighted Average Remaining Contractual Life	73 days
Options Outstanding, Weighted Average Exercise Price | $ / shares	$ 23.40
Options Exercisable, Shares	57,300
Options Exercisable, Weighted Average Exercise Price | $ / shares	$ 23.40
Exercise Price Range - $66.00 to $71.00
Options Outstanding and Exercisable [Abstract]
Range of Exercise Prices, lower range limit | $ / shares	66.00
Range of Exercise Prices, upper range limit | $ / shares	$ 71.00
Options Outstanding, Shares	60,000
Options Outstanding, Weighted Average Remaining Contractual Life	5 years 146 days
Options Outstanding, Weighted Average Exercise Price | $ / shares	$ 68.42
Options Exercisable, Shares	60,000
Options Exercisable, Weighted Average Exercise Price | $ / shares	$ 68.42
Exercise Price Range - $84.00 to $85.00
Options Outstanding and Exercisable [Abstract]
Range of Exercise Prices, lower range limit | $ / shares	84.00
Range of Exercise Prices, upper range limit | $ / shares	$ 85.00
Options Outstanding, Shares	870,750
Options Outstanding, Weighted Average Remaining Contractual Life	4 years 73 days
Options Outstanding, Weighted Average Exercise Price | $ / shares	$ 84.94
Options Exercisable, Shares	0
Options Exercisable, Weighted Average Exercise Price | $ / shares	$ 84.94
Stock Options [Member]
Share-based employee compensation, terms of award	The exercise price of stock option awards cannot be less than 100% of the market price of our common stock on the grant date.
Share-based employee compensation, vesting rights	The 2017 option awards vest 100% three years from grant date and have a maximum contractual life of six years. All prior option awards have a maximum contractual life of 10 years.
Restricted Stock [Member]
Share-based employee compensation, vesting rights	Generally, restricted shares vest ratably over five years from the grant date provided the employee remains employed by us.
Restricted Stock and PRSU Activity [Roll Forward]
January 1	2,859,373	3,802,105	4,349,105
Granted	815,810	966,919	1,100,396
Vested / Distributed	(944,048)	(1,757,269)	(1,438,386)
Forfeited	(177,233)	(152,382)	(209,010)
December 31	2,553,902	2,859,373	3,802,105
Restricted Stock and PRSU Activity, Weighted Average Grant Date Fair Value [Roll Forward]
January 1, Weighted Average Grant Date Fair Value | $ / shares	$ 68.85	$ 61.72
Granted, Weighted Average Grant Date Fair Value | $ / shares	67.62	74.10	$ 73.16
December 31, Weighted Average Grant Date Fair Value | $ / shares	$ 69.77	$ 68.85	$ 61.72
Performance Restricted Stock Units (PRSUs) [Member]
Share-based employee compensation, vesting rights	Each PRSU represents the right to receive one share of common stock on vesting. The ultimate number of PRSUs received by the employee depends on the Company's average return on equity over a three year period compared to the average return on equity of a peer group of principal competitors over the same period. The PRSUs vest three years from the grant date.
Restricted Stock and PRSU Activity [Roll Forward]
January 1	488,887	462,381	534,456
Granted	182,582	173,770	153,492
Vested / Distributed	(161,625)	(147,264)	(225,567)
December 31	509,844	488,887	462,381
Restricted Stock and PRSU Activity, Weighted Average Grant Date Fair Value [Roll Forward]
January 1, Weighted Average Grant Date Fair Value | $ / shares	$ 82.01	$ 77.05	$ 66.05
Granted, Weighted Average Grant Date Fair Value | $ / shares	73.72	84.94	83.23
Distributed, Weighted Average Grant Date Fair Value | $ / shares	77.68	69.89	55.20
December 31, Weighted Average Grant Date Fair Value | $ / shares	$ 80.41	$ 82.01	$ 77.05
Employee Stock Purchase Plan [Member]
Shares available for grant	8,675,351
Employee Stock Purchase Plan (ESPP) [Abstract]
Discount from market price	95.00%
Maximum percentage of eligible compensation allowable for purchase	10.00%
Shares issued in period	91,086	101,862	97,935
Proceeds from issuance of shares | $	$ 6.5	$ 7.6	$ 7.8
2013 Incentive Award Plan [Member]
Maximum of shares available for issuance	33,000,000
Stock awards other than options, conversion ratio	3.5
Shares available for grant	26,731,624
Stock awards other than options, shares available for grant	7,637,607