Investments in Qualified Affordable Housing Partnerships, Tax Credit and Other Investments, Net and Variable Interest Entities (Investments in Tax Credit and Other Investments, Net) (Details)	3 Months Ended			9 Months Ended
	Sep. 30, 2019 USD ($) credit	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) fund
Investments in Tax Credit and Other Investments, Net [Line Items]
Investments in tax credit and other investments, net	$ 211,603,000			$ 211,603,000		$ 231,635,000
Accrued expenses and other liabilities — Unfunded commitments	69,649,000			69,649,000		80,228,000
Amortization expense of tax credit and other investments	16,833,000		$ 20,789,000	58,477,000	$ 58,670,000
Unrealized gains (losses) recognized on marketable equity securities held	188,000		(185,000)	955,000	(798,000)
Tax credit investments
Investments in Tax Credit and Other Investments, Net [Line Items]
Marketable equity securities	31,700,000			31,700,000		31,200,000
Amortization of tax credit and other investments
Investments in Tax Credit and Other Investments, Net [Line Items]
Pre-tax impairment charge	1,700,000		$ 0	11,600,000	$ 0
DC Solar Tax Credit Investments
Investments in Tax Credit and Other Investments, Net [Line Items]
Investments in tax credit and other investments, net						$ 7,000,000.0
Number of solar energy tax credit funds | fund						4
DC Solar Tax Credit Investments | Accrued expenses and other liabilities - unfunded commitments
Investments in Tax Credit and Other Investments, Net [Line Items]
Accrued expenses and other liabilities — Unfunded commitments	0			$ 0		$ 0
DC Solar Tax Credit Investments | Amortization of tax credit and other investments
Investments in Tax Credit and Other Investments, Net [Line Items]
Pre-tax impairment charge		$ 7,000,000.0
Impaired CRA investments other than DC Solar | Amortization of tax credit and other investments
Investments in Tax Credit and Other Investments, Net [Line Items]
Pre-tax impairment charge	$ 1,700,000
Number of impaired tax credit investments | credit	2