Equity, Stock Repurchase (Details) - USD ($) shares in Millions, $ in Millions			1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended			23 Months Ended
	Apr. 24, 2018	Jan. 24, 2017	Jan. 31, 2021	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2018
Shareholders' Equity
Treasury stock retired (in dollars)						$ 0.0	$ 0.0	$ 0.0
Treasury stock, shares						1.0	0.8
Payments for shares repurchased (in dollars)						$ 641.3	$ 601.7	$ 935.2
2018 Stock Repurchase Program and 2017 Stock Repurchase Program
Shareholders' Equity
Number of shares repurchased								10.6
Payments for shares repurchased (in dollars)								$ 935.2
2018 Stock Repurchase Program
Shareholders' Equity
Value of shares authorized to be repurchased (in dollars)	$ 2,000.0
Repurchase of stock program, period	3 years
Number of shares repurchased					6.4	6.0	6.5	6.4
Payments for shares repurchased (in dollars)					$ 553.2	$ 641.3	$ 601.7	$ 553.2
Number of shares repurchased and retained in treasury						1.4	1.0	0.7
Payments for shares repurchased (in dollars)						$ 153.9	$ 87.6	$ 55.0
Number of shares repurchased and retired						4.6	5.5	5.7
Payments for shares repurchased and retired (in dollars)						$ 487.4	$ 514.1	$ 498.2
2017 Stock Repurchase Program
Shareholders' Equity
Value of shares authorized to be repurchased (in dollars)		$ 1,000.0
Repurchase of stock program, period		2 years
Number of shares repurchased and retired				4.2
Payments for shares repurchased and retired (in dollars)				$ 382.0					$ 1,000.0
Subsequent Event | 2018 Stock Repurchase Program
Shareholders' Equity
Payments for shares repurchased (in dollars)			$ 4.0
Value of shares remaining that may be repurchased under the stock repurchase program (in dollars)			$ 199.8