CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock [Member]	Unearned KSOP Contributions [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Losses [Member]
Balance at Dec. 31, 2013	$ 547.6	$ 0.1	$ (0.3)	$ 1,202.1	$ (1,864.9)	$ 1,254.1	$ (43.5)
Balance (in shares) at Dec. 31, 2013	544,003,038
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 400.0					400.0
Total other comprehensive income (loss)	(37.0)						(37.0)
Treasury stock acquired	(775.4)			(100.0)	(675.4)
KSOP shares earned (181,198 shares reissued from treasury stock)	15.3		0.1	15.2
Stock options exercised, including tax benefit	39.8			34.0	5.8
Restricted stock lapsed, including tax benefit	0.5			(0.2)	0.7
Employee stock purchase plan	1.5			1.4	0.1
Stock based compensation	20.0			20.0
Net share settlement from restricted stock awards	(1.6)			(1.6)
Other stock issuances	0.3			0.3
Balance at Dec. 31, 2014	$ 211.0	0.1	(0.2)	1,171.2	(2,533.7)	1,654.1	(80.5)
Balance (in shares) at Dec. 31, 2014	544,003,038
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 507.6					507.6
Total other comprehensive income (loss)	(161.5)						(161.5)
Treasury stock acquired	(20.5)			100.0	(120.5)
KSOP shares earned (181,198 shares reissued from treasury stock)	14.1		0.2	13.6	0.3
Shares issued from equity offering	720.9			651.3	69.6
Stock options exercised, including tax benefit	69.2			57.5	11.7
Restricted stock lapsed, including tax benefit	1.3			0.1	1.2
Employee stock purchase plan	1.8			1.6	0.2
Stock based compensation	30.1			30.1
Net share settlement from restricted stock awards	(2.4)			(2.4)
Other stock issuances	0.4			0.4
Balance at Dec. 31, 2015	$ 1,372.0	0.1	0.0	2,023.4	(2,571.2)	2,161.7	(242.0)
Balance (in shares) at Dec. 31, 2015	544,003,038
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 591.2					591.2
Total other comprehensive income (loss)	(408.8)						(408.8)
Treasury stock acquired	(333.3)				(333.3)
KSOP shares earned (181,198 shares reissued from treasury stock)	14.5			13.2	1.3
Stock options exercised, including tax benefit	66.4			56.2	10.2
Restricted stock lapsed, including tax benefit	1.2				1.2
Employee stock purchase plan	2.3			2.1	0.2
Stock based compensation	29.9			29.9
Net share settlement from restricted stock awards	(3.1)			(3.1)
Other stock issuances	0.1			(0.1)	0.2
Balance at Dec. 31, 2016	$ 1,332.4	$ 0.1	$ 0.0	$ 2,121.6	$ (2,891.4)	$ 2,752.9	$ (650.8)
Balance (in shares) at Dec. 31, 2016	544,003,038