Summary of Significant Accounting Policies, Stock Split (Details) $ in Millions	Jan. 27, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Cumulative-effect adjustment to equity		$ 6,360.1	$ 5,451.9	$ 4,596.2	$ 4,064.2
Stock split conversion ratio	2
Common Stock
Cumulative-effect adjustment to equity		0.6	0.6	0.6	0.6
Additional Paid in Capital
Cumulative-effect adjustment to equity		2,409.0	2,068.1	1,683.0	1,432.9
Retained Earnings
Cumulative-effect adjustment to equity		4,278.9	3,705.4	3,348.4	3,028.7
Retroactive adjustment | Common Stock
Cumulative-effect adjustment to equity	$ 0.3	0.3	0.3	0.3	0.3
Retroactive adjustment | Additional Paid in Capital
Cumulative-effect adjustment to equity	$ (0.3)	$ (0.3)	$ (0.3)	$ (0.3)	$ (0.3)