Qualified Affordable Housing Projects and Other Tax Credit Investments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Investment Holdings [Line Items]
Investment	$ 61,487		$ 61,487		$ 59,661
Unfunded Commitment	27,514		27,514		25,926
Amortization Expense	1,063	$ 1,359	7,355	$ 2,412
Tax Expense (Benefit) Recognized	(2,682)	(1,575)	(5,457)	(2,862)
LIHTC
Investment Holdings [Line Items]
Investment, Proportional amortization	28,083		28,083		29,735
Unfunded Commitment, Proportional amortization	2,646		2,646		3,911
Amortization Expense	776	791	1,553	1,584
Tax Expense (Benefit) Recognized	(1,019)	(1,042)	(2,038)	(2,085)
FHTC
Investment Holdings [Line Items]
Investment, Equity	25,760		25,760		22,403
Unfunded Commitment, Equity	21,778		21,778		17,886
Amortization Expense	0		5,143
Tax Expense (Benefit) Recognized	(1,356)		(2,712)
Renewable Energy
Investment Holdings [Line Items]
Investment, Equity	7,644		7,644		7,523
Unfunded Commitment, Equity	3,090		3,090		$ 4,129
Amortization Expense	287	568	659	828
Tax Expense (Benefit) Recognized	$ (307)	$ (533)	$ (707)	$ (777)