Condensed Consolidated Statements of Changes In Stockholders' Equity (Unaudited) - USD ($) $ in Millions		Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Treasury Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] AOCI Attributable to Parent [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2018								544,003,038
Balance at Dec. 31, 2018								$ 0.1	$ 2,283.0	$ (3,563.2)	$ 3,942.6	$ (591.9)	$ 2,070.6
Net income								0.0	0.0	0.0	284.8	0.0	284.8
Common stock dividend								0.0	0.0	0.0	(82.1)	0.0	(82.1)
Other comprehensive income (loss)								0.0	0.0	0.0	0.0	(0.3)	(0.3)
Treasury stock acquired								0.0	0.0	(125.0)	0.0	0.0	(125.0)
Stock options exercised								0.0	31.2	6.9	0.0	0.0	38.1
Restricted stock lapsed								0.0	(1.6)	1.6	0.0	0.0	0.0
Stock-based compensation expense								0.0	27.6	0.0	0.0	0.0	27.6
Net share settlement from restricted stock awards								0.0	(5.1)	0.0	0.0	0.0	(5.1)
Other stock issuances								$ 0.0	1.8	0.3	0.0	0.0	2.1
Balance (in shares) at Jun. 30, 2019								544,003,038
Balance at Jun. 30, 2019								$ 0.1	2,336.9	(3,679.4)	4,145.3	(592.2)	2,210.7
Balance (in shares) at Mar. 31, 2019								544,003,038
Balance at Mar. 31, 2019								$ 0.1	2,301.9	(3,635.2)	4,036.0	(532.3)	2,170.5
Net income								0.0	0.0	0.0	150.4	0.0	150.4
Common stock dividend	[1]							0.0	0.0	0.0	(41.1)	0.0	(41.1)
Other comprehensive income (loss)								0.0	0.0	0.0	0.0	(59.9)	(59.9)
Treasury stock acquired								0.0	0.0	(50.0)	0.0	0.0	(50.0)
Stock options exercised								0.0	22.5	4.0	0.0	0.0	26.5
Restricted stock lapsed								0.0	(1.6)	1.6	0.0	0.0	0.0
Stock-based compensation expense								0.0	18.4	0.0	0.0	0.0	18.4
Net share settlement from restricted stock awards								0.0	(5.1)	0.0	0.0	0.0	(5.1)
Other stock issuances								$ 0.0	0.8	0.2	0.0	0.0	1.0
Balance (in shares) at Jun. 30, 2019								544,003,038
Balance at Jun. 30, 2019								$ 0.1	2,336.9	(3,679.4)	4,145.3	(592.2)	2,210.7
Balance (in shares) at Dec. 31, 2019								544,003,038
Balance at Dec. 31, 2019		$ 0.0	$ 0.0	$ 0.0	$ (2.4)	$ 0.0	$ (2.4)	$ 0.1	2,369.1	(3,849.9)	4,228.4	(486.9)	2,260.8
Net income								0.0	0.0	0.0	350.7	0.0	350.7
Common stock dividend								0.0	0.0	0.0	(87.9)	0.0	(87.9)
Other comprehensive income (loss)								0.0	0.0	0.0	0.0	(170.3)	(170.3)
Treasury stock acquired								0.0	0.0	(248.8)	0.0	0.0	(248.8)
Stock options exercised								0.0	37.2	8.6	0.0	0.0	45.8
Restricted stock lapsed								0.0	(1.5)	1.5	0.0	0.0	0.0
Stock-based compensation expense								0.0	29.1	0.0	0.0	0.0	29.1
Net share settlement from restricted stock awards								0.0	(3.5)	0.0	0.0	0.0	(3.5)
Other stock issuances								$ 0.0	2.4	0.2	0.0	0.0	2.6
Balance (in shares) at Jun. 30, 2020								544,003,038
Balance at Jun. 30, 2020								$ 0.1	2,432.8	(4,088.4)	4,488.8	(657.2)	2,176.1
Balance (in shares) at Mar. 31, 2020								544,003,038
Balance at Mar. 31, 2020								$ 0.1	2,404.6	(4,018.9)	4,353.4	(658.7)	2,080.5
Net income								0.0	0.0	0.0	179.0	0.0	179.0
Common stock dividend	[1]							0.0	0.0	0.0	(43.6)	0.0	(43.6)
Other comprehensive income (loss)								0.0	0.0	0.0	0.0	1.5	1.5
Treasury stock acquired								0.0	0.0	(75.0)	0.0	0.0	(75.0)
Stock options exercised								0.0	22.4	3.9	0.0	0.0	26.3
Restricted stock lapsed								0.0	(1.5)	1.5	0.0	0.0	0.0
Stock-based compensation expense								0.0	9.5	0.0	0.0	0.0	9.5
Net share settlement from restricted stock awards								0.0	(3.5)	0.0	0.0	0.0	(3.5)
Other stock issuances								$ 0.0	1.3	0.1	0.0	0.0	1.4
Balance (in shares) at Jun. 30, 2020								544,003,038
Balance at Jun. 30, 2020								$ 0.1	$ 2,432.8	$ (4,088.4)	$ 4,488.8	$ (657.2)	$ 2,176.1

[1] Refer to Note 10. Stockholders' Equity for discussion related to quarterly cash dividends declared per share