Fair Value Disclosures (Details 2) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Impaired loans
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
Asset measured on nonrecurring basis, reported fair value	$ 72.6		$ 109.6
Asset measured on nonrecurring basis, carrying value	96.3		$ 145.4
Asset measured on nonrecurring basis, specific valuation allowance	$ 23.7	$ 35.8
Measurement Input, Discount Rate
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
Loans Held-for-sale, measurement input	0.954		0.941
Minimum | Tax-exempt asset-backed securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, term	6 years 6 months
Minimum | Credit risk transfer securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, term	7 years
Minimum | Measurement Input, Discount Rate | Tax-exempt asset-backed securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, measurement input	0.0352
Minimum | Measurement Input, Discount Rate | Credit risk transfer securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, measurement input	0.0299
Maximum | Tax-exempt asset-backed securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, term	7 years 8 months 12 days
Maximum | Credit risk transfer securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, term	11 years 1 month 6 days
Maximum | Measurement Input, Discount Rate | Tax-exempt asset-backed securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, measurement input	0.0355
Maximum | Measurement Input, Discount Rate | Credit risk transfer securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, measurement input	0.0720
Weighted Average | Measurement Input, Discount Rate | Tax-exempt asset-backed securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, measurement input	0.0354		0.0299
AFS, term	7 years 1 month 6 days		7 years
Weighted Average | Measurement Input, Discount Rate | Credit risk transfer securities
Fair Value Assets Measured On Non Recurring Basis Unobservable Input Reconciliation [Line Items]
AFS, measurement input	0.0439		0.0454
AFS, term	8 years 4 months 24 days		9 years 3 months 18 days