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		12 Months Ended			60 Months Ended
	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) fund
Investments in Tax Credit and Other Investments, Net
Investments in tax credit and other investments, net	$ 254,140,000		$ 254,140,000	$ 231,635,000		$ 231,635,000
Accrued expenses and other liabilities — Unfunded commitments	113,515,000		113,515,000	80,228,000		80,228,000
Amortization of tax credit and other investments			85,515,000	89,628,000	$ 87,950,000
Equity securities without readily determinable fair values at carrying value	19,100,000		19,100,000	14,200,000		14,200,000
Price adjustment to equity securities			0	0
Available-for-sale debt securities, Fair Value	3,317,214,000		3,317,214,000	2,741,847,000		2,741,847,000
DC Solar Tax Credit Investments
Investments in Tax Credit and Other Investments, Net
Investments in tax credit and other investments, net				7,000,000.0		$ 7,000,000.0
Number of tax credit funds | fund						4
Pre-tax impairment charge or recovery	1,600,000		1,600,000
Expected Future Cash Flows		$ 0
Accrued Expenses And Other Liabilities, Unfunded Commitments | DC Solar Tax Credit Investments
Investments in Tax Credit and Other Investments, Net
Accrued expenses and other liabilities — Unfunded commitments	0		0	0		$ 0
Amortization of Tax Credit And Other Investments
Investments in Tax Credit and Other Investments, Net
Pre-tax impairment charge			14,600,000
Pre-tax impairment charge or recovery				$ 0
Amortization of Tax Credit And Other Investments | DC Solar Tax Credit Investments
Investments in Tax Credit and Other Investments, Net
Pre-tax impairment charge		$ 7,000,000.0
Collateralized loan obligations (“CLOs”)
Investments in Tax Credit and Other Investments, Net
Available-for-sale debt securities, Fair Value	$ 284,706,000		$ 284,706,000