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		6 Months Ended
	Jun. 30, 2019 USD ($) fund	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) fund	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Investments in Tax Credit and Other Investments, Net [Line Items]
Investments in tax credit and other investments, net	$ 210,387,000		$ 210,387,000		$ 231,635,000
Accrued expenses and other liabilities — Unfunded commitments	73,369,000		73,369,000		80,228,000
Amortization expense of tax credit and other investments	16,739,000	$ 20,481,000	41,644,000	$ 37,881,000
Unrealized gains (losses) recognized on marketable equity securities held	375,000	$ (159,000)	767,000	$ (613,000)
Pre-tax impairment charge	2,900,000		9,900,000
Tax credit investments
Investments in Tax Credit and Other Investments, Net [Line Items]
Marketable equity securities	$ 31,400,000		$ 31,400,000		31,200,000
DC Solar Tax Credit Investments
Investments in Tax Credit and Other Investments, Net [Line Items]
Number of solar energy tax credit funds | fund	4		4
Investments in tax credit and other investments, net					7,000,000.0
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