Significant Accounting Policies Schedule of New Accounting Pronouncements (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle
Other Assets	$ 884.0		$ 789.0
Deferred Income Tax Assets, Net	0.0		109.9
Other Liabilities	1,880.5		1,762.8
Income Tax Payable	256.7		24.0
Retained Earnings	$ 10,728.7		9,863.1
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle
Other Assets		$ 906.7	789.0
Deferred Income Tax Assets, Net		109.5	109.9
Other Liabilities		1,884.8	1,762.8
Income Tax Payable		22.7	24.0
Retained Earnings		9,859.7	$ 9,863.1
Accounting Standards Update 2016-02 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Other Assets		117.7
Deferred Income Tax Assets, Net		(0.4)
Other Liabilities		122.0
Income Tax Payable		(1.3)
Retained Earnings		$ (3.4)