Qualified Affordable Housing Projects and Other Tax Credit Investments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investment Holdings [Line Items]
Investment	$ 62,000	$ 59,661
Unfunded Commitment	30,105	25,926
Amortization Expense	21,893	5,917	$ 25,534
Tax Expense (Benefit) Recognized	(24,875)	(7,086)	(29,377)
LIHTC
Investment Holdings [Line Items]
Investment, Proportional amortization	33,609	29,735
Unfunded commitment, Proportional amortization	6,845	3,911
Amortization Expense	3,105	3,168	2,585
Tax Expense (Benefit) Recognized	(4,071)	(4,102)	(3,349)
FHTC
Investment Holdings [Line Items]
Investment, Equity	18,660	22,403
Unfunded commitment, Equity	22,398	17,886
Amortization Expense	13,237	1,113	9,206
Tax Expense (Benefit) Recognized	(15,582)	(1,244)	(10,775)
New Markets Tax Credit
Investment Holdings [Line Items]
Investment, Proportional amortization	6,120	0
Unfunded commitment, Proportional amortization	0	0
Amortization Expense	900
Tax Expense (Benefit) Recognized	(1,100)
Renewable Energy
Investment Holdings [Line Items]
Investment, Equity	3,611	7,523
Unfunded commitment, Equity	862	4,129
Amortization Expense	4,651	1,623	13,056
Tax Expense (Benefit) Recognized	$ (4,122)	(1,740)	(14,566)
CReED
Investment Holdings [Line Items]
Amortization Expense		13	687
Tax Expense (Benefit) Recognized		$ 0	$ (687)