Share-Based Compensation Plans (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) shares $ / shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares
Share-based employee compensation expense | $	$ 93.4	$ 99.4	$ 93.5
Unamortized share-based employee compensation, amortization period	5 years
Unamortized share-based employee compensation | $	$ 173.2
Option Activity [Roll Forward]
January 1	1,140,547	1,652,140	2,643,680
Granted	0	0	60,000
Exercised	(420,790)	(511,593)	(1,046,540)
Forfeited	0	0	(5,000)
December 31	719,757	1,140,547	1,652,140
Exercisable December 31	695,757	1,074,547	1,526,140
January 1, Weighted Average Exercise Price | $ / shares	$ 28.86	$ 27.97	$ 26.39
Granted, Weighted Average Exercise Price | $ / shares			66.16
Exercised, Weighted Average Exercise Price | $ / shares	30.56	25.98	26.19
Forfeited, Weighted Average Exercise Price | $ / shares			23.40
December 31, Weighted Average Exercise Price | $ / shares	27.88	28.86	27.97
Exercisable December 31, Weighted Average Exercise Price | $ / shares	$ 26.54	$ 26.47	$ 24.95
Options Outstanding and Exercisable [Abstract]
Options Outstanding, Shares	719,757
Options Exercisable, Shares	695,757
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	647,757
Options Outstanding, Weighted Average Remaining Contractual Life	2 years 73 days
Options Outstanding, Weighted Average Exercise Price | $ / shares	$ 23.40
Options Exercisable, Shares	647,757
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	72,000
Options Outstanding, Weighted Average Remaining Contractual Life	7 years 146 days
Options Outstanding, Weighted Average Exercise Price | $ / shares	$ 68.04
Options Exercisable, Shares	48,000
Options Exercisable, Weighted Average Exercise Price | $ / shares	$ 68.99
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 and the option term cannot exceed ten years from the grant date.
Share-based employee compensation, vesting rights	Generally, stock option awards vest over three years from the grant date as follows: 30%, 30% and 40%.
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	4,349,105	5,040,641	6,090,697
Granted	1,100,396	1,208,964	915,922
Vested / Distributed	(1,438,386)	(1,631,343)	(1,619,444)
Forfeited	(209,010)	(269,157)	(346,534)
December 31	3,802,105	4,349,105	5,040,641
Restricted Stock and PRSU Activity, Weighted Average Grant Date Fair Value [Roll Forward]
January 1, Weighted Average Grant Date Fair Value | $ / shares	$ 55.08	$ 50.98
Granted, Weighted Average Grant Date Fair Value | $ / shares	73.16	64.49	$ 64.92
December 31, Weighted Average Grant Date Fair Value | $ / shares	$ 61.72	$ 55.08	$ 50.98
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	534,456	622,859	681,555
Granted	153,492	161,625	188,621
Vested / Distributed	(225,567)	(239,387)	(165,562)
Forfeited	0	(10,641)	(81,755)
December 31	462,381	534,456	622,859
Restricted Stock and PRSU Activity, Weighted Average Grant Date Fair Value [Roll Forward]
January 1, Weighted Average Grant Date Fair Value | $ / shares	$ 66.05	$ 56.16	$ 51.19
Granted, Weighted Average Grant Date Fair Value | $ / shares	83.23	77.68	69.89
Distributed, Weighted Average Grant Date Fair Value | $ / shares	55.20	48.94	48.56
Forfeited, Weighted Average Grant Date Fair Value | $ / shares	0.00	48.87	61.76
December 31, Weighted Average Grant Date Fair Value | $ / shares	$ 77.05	$ 66.05	$ 56.16
Employee Stock Purchase Plan [Member]
Shares available for grant	8,868,299
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	97,935	111,849	113,293
Proceeds from issuance of shares | $	$ 7.8	$ 7.8	$ 8.0
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	30,308,073
Stock awards other than options, shares available for grant	8,659,449