Variable Interest Entities (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Variable Interest Entity [Line Items]
Exposure to loss from liquidity arrangements and obligations to purchase assets	$ 0
Affordable housing tax credits and other tax benefits	16,300,000	$ 16,400,000
Fair value, investments, entities that calculate net asset value per share, unfunded commitments	74,600,000		$ 0
Leveraged Leasing Transactions
Variable Interest Entity [Line Items]
VIE carrying amounts	42,800,000		42,600,000
Exposure to loss from liquidity arrangements and obligations to purchase assets	$ 0
Leveraged Leasing Transactions | Lower Limit
Variable Interest Entity [Line Items]
Funding of assets cost via equity interest	20.00%
Funding of asset's cost via third party non recourse debt holders	70.00%
Leveraged Leasing Transactions | Upper Limit
Variable Interest Entity [Line Items]
Funding of assets cost via equity interest	30.00%
Funding of asset's cost via third party non recourse debt holders	80.00%
Other Assets
Variable Interest Entity [Line Items]
Investments in community development projects, carrying amount, assets	$ 746,200,000		749,300,000
Alternative investment	100,000,000.0		112,000,000.0
Other Assets | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
VIE carrying amounts	697,800,000		700,300,000
Other Liabilities
Variable Interest Entity [Line Items]
Investments in community development projects, carrying amount, liabilities	362,700,000		376,200,000
Other Liabilities | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Variable interest entity, nonconsolidated, carrying amount, liabilities	$ 342,500,000		$ 354,300,000