Shareholders' Equity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2018
Statement [Line Items]
Purchase for treasury	$ 4,400.0	$ 4,150.0	$ 359.8
Preferred stock, shares authorized (in shares)	5,000,000.0
Shares issued (in shares)	0	0
Shares held in employee trust (in shares)	50,000,000.0	50,000,000
Employee benefit trust	$ 3,013.2	$ 3,013.2
2018 Repurchase Program
Statement [Line Items]
Remaining authorized repurchase amount	$ 1,500.0
Stock repurchase program, authorized amount				$ 8,000.0