Variable Interest Entities (Income Tax Credits and Other Tax Benefits and Amortization Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Variable Interest Entity [Line Items]
Income Tax Credits and Other Income Tax Benefits	$ 27.0	$ 28.4	$ 80.6	$ 85.1
Amortization Expense	24.0	24.6	71.8	73.6
Affordable Housing
Variable Interest Entity [Line Items]
Income Tax Credits and Other Income Tax Benefits	21.9	22.5	65.5	67.3
Amortization Expense	19.6	19.9	58.5	59.5
New Markets
Variable Interest Entity [Line Items]
Income Tax Credits and Other Income Tax Benefits	5.1	5.9	15.1	17.8
Amortization Expense	$ 4.4	$ 4.7	$ 13.3	$ 14.1