Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Preferred Stock	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock, at Cost
Beginning balance at Dec. 31, 2018	$ 5,946.6	$ 325.0	$ 1.6	$ 6,810.8	$ 1,924.4	$ (178.3)	$ (2,936.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	118.9				118.9
Other comprehensive income, net of tax	53.1					53.1
Dividends paid	(25.7)				(25.7)
Share repurchases	(179.7)						(179.7)
Amortization of stock compensation expenses	(4.4)			13.7			(18.1)
Employee stock purchase plan	0.7			0.7
Ending balance at Mar. 31, 2019	5,909.5	325.0	1.6	6,825.2	2,017.6	(125.2)	(3,134.7)
Beginning balance at Dec. 31, 2019	6,339.0	525.0	1.6	6,853.7	2,307.6	(52.1)	(3,296.8)
Adoption of Accounting Standard Update at Dec. 31, 2019	(82.4)				(82.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(624.3)				(624.3)
Other comprehensive income, net of tax	118.9					118.9
Dividends paid	(38.7)				(38.7)
Issuance of common stock - acquisition	141.2				(10.1)		151.3
Amortization of stock compensation expenses	6.3			18.8			(12.5)
Employee stock purchase plan	0.8			0.8
Ending balance at Mar. 31, 2020	$ 5,860.8	$ 525.0	$ 1.6	$ 6,873.3	$ 1,552.1	$ 66.8	$ (3,158.0)