STATEMENTS OF CONSOLIDATED SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Other Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Adjustment
Beginning balance at Dec. 31, 2018	$ 3,730.7		$ 118.4	$ 2,896.4	$ 6,246.5		$ (4,900.7)	$ (629.9)	$ (8.3)
Beginning balance (ASU 2016-02) at Dec. 31, 2018		$ (8.4)				$ (8.4)
Beginning balance (ASU 2018-02) at Dec. 31, 2018						8.3			(8.3)
Shareholders' Equity [Roll Forward]
Net income	245.2				245.2
Other comprehensive income (loss)	6.0							6.0
Treasury stock purchased	(305.1)						(305.1)
Treasury stock transferred to qualified replacement plan	(131.8)						(131.8)
Stock-based compensation activity	26.6		0.3	47.6			(21.3)
Other adjustments	1.7			1.6	0.1
Cash dividends	(104.8)				(104.8)
Ending balance at Mar. 31, 2019	3,460.1		118.7	2,945.6	6,386.9		(5,358.9)	(632.2)
Beginning balance at Dec. 31, 2018	3,730.7		118.4	2,896.4	6,246.5		(4,900.7)	(629.9)	(8.3)
Beginning balance (ASU 2016-02) at Dec. 31, 2018		(8.4)				(8.4)
Beginning balance (ASU 2018-02) at Dec. 31, 2018						8.3			$ (8.3)
Shareholders' Equity [Roll Forward]
Net income	716.2
Other comprehensive income (loss)	7.4
Ending balance at Jun. 30, 2019	3,747.5		118.9	3,010.7	6,753.0		(5,504.3)	(630.8)
Beginning balance at Mar. 31, 2019	3,460.1		118.7	2,945.6	6,386.9		(5,358.9)	(632.2)
Shareholders' Equity [Roll Forward]
Net income	471.0				471.0
Other comprehensive income (loss)	1.4							1.4
Treasury stock purchased	(145.4)						(145.4)
Stock-based compensation activity	65.2		0.2	65.0
Other adjustments	0.2			0.1	0.1
Cash dividends	(105.0)				(105.0)
Ending balance at Jun. 30, 2019	3,747.5		118.9	3,010.7	6,753.0		(5,504.3)	(630.8)
Beginning balance at Dec. 31, 2019	4,123.3	(3.0)	119.4	3,153.0	7,366.9	(3.0)	(5,836.5)	(679.5)
Shareholders' Equity [Roll Forward]
Net income	321.7				321.7
Other comprehensive income (loss)	(221.6)							(221.6)
Treasury stock purchased	(890.3)						(890.3)
Treasury stock issued	57.4			13.5			43.9
Stock-based compensation activity	24.2		0.3	48.7			(24.8)
Other adjustments	0.3			0.3
Cash dividends	(122.9)				(122.9)
Ending balance at Mar. 31, 2020	3,289.1		119.7	3,215.5	7,562.7		(6,707.7)	(901.1)
Beginning balance at Dec. 31, 2019	4,123.3	$ (3.0)	119.4	3,153.0	7,366.9	$ (3.0)	(5,836.5)	(679.5)
Shareholders' Equity [Roll Forward]
Net income	917.6
Other comprehensive income (loss)	(187.7)
Ending balance at Jun. 30, 2020	3,869.9		120.0	3,289.1	8,036.0		(6,708.0)	(867.2)
Beginning balance at Mar. 31, 2020	3,289.1		119.7	3,215.5	7,562.7		(6,707.7)	(901.1)
Shareholders' Equity [Roll Forward]
Net income	595.9				595.9
Other comprehensive income (loss)	33.9							33.9
Stock-based compensation activity	73.3		0.3	73.3			(0.3)
Other adjustments	0.4			0.3	0.1
Cash dividends	(122.7)				(122.7)
Ending balance at Jun. 30, 2020	$ 3,869.9		$ 120.0	$ 3,289.1	$ 8,036.0		$ (6,708.0)	$ (867.2)