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, 2020 USD ($) credit	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) credit	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Investments in Tax Credit and Other Investments, Net [Line Items]
Investments in tax credit and other investments, net	$ 251,318,000		$ 251,318,000		$ 254,140,000
Accrued expenses and other liabilities — Unfunded commitments	106,969,000		106,969,000		113,515,000
Amortization expense of tax credit and other investments	24,759,000	$ 16,739,000	42,084,000	$ 41,644,000
Unrealized gains recognized on equity securities with readily determinable fair values	720,000	375,000	758,000	767,000
Equity securities without readily determinable fair values	18,800,000		18,800,000		19,100,000
Adjustments to equity securities without readily determinable fair values	0	0	0	0
AFS debt securities	3,884,574,000		3,884,574,000		3,317,214,000
Collateralized loan obligations (“CLOs”)
Investments in Tax Credit and Other Investments, Net [Line Items]
AFS debt securities	273,979,000		273,979,000		284,706,000
Tax credit investments
Investments in Tax Credit and Other Investments, Net [Line Items]
Equity securities with readily determinable fair values	31,100,000		31,100,000		$ 31,700,000
Amortization of tax credit and other investments
Investments in Tax Credit and Other Investments, Net [Line Items]
Tax Credit Investments, Pre-tax Impairment Recovery	109,000	0	$ 259,000	0
OTTI charge	$ 733,000	$ 2,900,000		$ 9,900,000
Historic Tax Credit Investment
Investments in Tax Credit and Other Investments, Net [Line Items]
Number of recovered historic tax credit investments | credit	1		2
CRA Investment
Investments in Tax Credit and Other Investments, Net [Line Items]
Number of recovered historic tax credit investments | credit	1