Income Taxes Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Tax Credit Carryforward, Amount	$ 10,000,000.0
Amortization Method Qualified Affordable Housing Project Investments	50,000,000	$ 57,000,000
Qualified Affordable Housing Project Investments, Commitment	4,000,000	8,000,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	79,000,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	369,100,000	368,900,000	$ 78,200,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	16,300,000	11,400,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, net of tax	4,900,000	$ 4,900,000	$ 3,200,000
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards	3,000,000.0
State and Local Jurisdiction [Member]
Operating Loss Carryforwards	110,700,000
Tax Credit Carryforward, Amount	100,700,000
Maximum [Member] | State and Local Jurisdiction [Member]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	358,700,000
Minimum | State and Local Jurisdiction [Member]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 0