CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2015	$ 2,023.2	$ 292.8	$ (1,103.7)	$ 230.0	$ 2,650.0	$ (45.9)
Beginning Balance (in shares) at Dec. 31, 2015		292.8	(32.8)
Net Income	348.6	$ 0.0	$ 0.0	0.0	348.6	0.0
Other comprehensive income (loss)	(5.9)	0.0	0.0	0.0	0.0	(5.9)
Cash dividends	(137.4)	0.0	0.0	0.0	(137.4)	0.0
Stock purchases	(200.0)	$ 0.0	$ (200.0)	0.0	0.0	0.0
Stock purchases (in shares)		0.0	(4.5)
Stock based compensation expense and stock option plan transactions, including related income tax benefits	91.5	$ 0.0	$ 72.7	18.8	0.0	0.0
Stock based compensation expense and stock option plan transactions, including related income tax benefits (in shares)		0.0	2.8
Ending Balance at Sep. 30, 2016	2,120.0	$ 292.8	$ (1,231.0)	248.8	2,861.2	(51.8)
Ending Balance (in shares) at Sep. 30, 2016		292.8	(34.5)
Beginning Balance at Dec. 31, 2016	1,977.9	$ 292.8	$ (1,428.5)	251.4	2,926.0	(63.8)
Beginning Balance (in shares) at Dec. 31, 2016		292.8	(38.9)
Net Income	337.8	$ 0.0	$ 0.0	0.0	337.8	0.0
Other comprehensive income (loss)	28.3	0.0	0.0	0.0	0.0	28.3
Cash dividends	(143.2)	0.0	0.0	0.0	(143.2)	0.0
Stock purchases	$ (300.0)	$ 0.0	$ (300.0)	0.0	0.0	0.0
Stock purchases (in shares)	(6.0)	0.0	(6.0)
Stock based compensation expense and stock option plan transactions, including related income tax benefits	$ 52.3	$ 0.0	$ 43.2	9.1	0.0	0.0
Stock based compensation expense and stock option plan transactions, including related income tax benefits (in shares)		0.0	1.8
Ending Balance at Sep. 30, 2017	$ 1,953.1	$ 292.8	$ (1,685.3)	$ 260.5	$ 3,120.6	$ (35.5)
Ending Balance (in shares) at Sep. 30, 2017		292.8	(43.1)