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, 2014	$ 2,101.9	$ 292.8	$ (789.5)	$ 218.4	$ 2,414.9	$ (34.7)
Beginning Balance (in shares) at Dec. 31, 2014		292.8	(26.2)
Net Income	301.3	$ 0.0	$ 0.0	0.0	301.3	0.0
Other comprehensive income (loss)	(10.2)	0.0	0.0	0.0	0.0	(10.2)
Cash dividends	(131.4)	0.0	0.0	0.0	(131.4)	0.0
Stock purchases	(263.1)	$ 0.0	$ (263.1)	0.0	0.0	0.0
Stock purchases (in shares)		0.0	(6.4)
Transfer of stock for settlement of share repurchase agreement	0.0	$ 0.0	$ 4.1	(4.1)	0.0	0.0
Transfer of stock for settlement of share repurchase agreement (in shares)		0.0	0.2
Stock based compensation expense and stock option plan transactions, including related income tax benefits	51.1	$ 0.0	$ 37.7	13.4	0.0	0.0
Stock based compensation expense and stock option plan transactions, including related income tax benefits (in shares)		0.0	1.6
Ending Balance at Sep. 30, 2015	2,049.6	$ 292.8	$ (1,010.8)	227.7	2,584.8	(44.9)
Ending Balance (in shares) at Sep. 30, 2015		292.8	(30.8)
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)