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Funding of asset's cost via an equity ownership in a trust.

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Investments In Community Development Projects, Carrying Amount, Assets

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Investments In Community Development Projects, Carrying Amount, Liabilities

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Amount of affordable housing tax credits and other tax benefits recognized.

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Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund.

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The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

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The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

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Carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

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Variable Interest Entities (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Variable Interest Entity [Line Items]
Exposure to loss from liquidity arrangements and obligations to purchase assets	$ 0		$ 0
Affordable housing tax credits and other tax benefits	15,600,000	$ 12,500,000	45,200,000	$ 38,300,000
Fair value, investments, entities that calculate net asset value per Share, unfunded commitments	98,400,000.0		98,400,000.0		$ 0
Leveraged Leasing Transactions
Variable Interest Entity [Line Items]
VIE carrying amounts	83,600,000		83,600,000		131,000,000
Exposure to loss from liquidity arrangements and obligations to purchase assets	$ 0		$ 0
Leveraged Leasing Transactions \| Lower Limit
Variable Interest Entity [Line Items]
Funding of assets cost via equity interest	20.00%		20.00%
Funding of asset's cost via third party non recourse debt holders	70.00%		70.00%
Leveraged Leasing Transactions \| Upper Limit
Variable Interest Entity [Line Items]
Funding of assets cost via equity interest	30.00%		30.00%
Funding of asset's cost via third party non recourse debt holders	80.00%		80.00%
Accounting Standards Update 2015-02
Variable Interest Entity [Line Items]
Money market mutual funds fees waived		$ 300,000		$ 700,000
Other Assets
Variable Interest Entity [Line Items]
Investments in community development projects, carrying amount, assets	$ 541,100,000		$ 541,100,000		415,300,000
Alternative Investment	36,300,000		36,300,000		10,000,000
Other Assets \| Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
VIE carrying amounts	487,600,000		487,600,000		386,100,000
Other Liabilities
Variable Interest Entity [Line Items]
Investments in community development projects, carrying amount, liabilities	291,700,000		291,700,000		241,100,000
Other Liabilities \| Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Variable interest entity, nonconsolidated, carrying amount, liabilities	$ 247,500,000		$ 247,500,000		$ 215,200,000