Qualified Affordable Housing Projects and Other Tax Credit Investments - Schedule of Qualified Affordable Housing Projects and Other Tax Credit Investments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Investment Holdings [Line Items]
Total	$ 61,235		$ 61,235		$ 54,404
Total	29,196		29,196		38,548
Amortization Expense	2,004	$ 9,873	4,415	$ 23,730
Tax Expense (Benefit) Recognized	(2,306)	(5,199)	(5,167)	(17,054)
LIHTC [Member]
Investment Holdings [Line Items]
Proportional amortization method of investment	30,577		30,577		28,396
Unfunded commitment, Proportional amortization	3,973		3,973		2,238
Amortization Expense	793	640	2,376	1,923
Tax Expense (Benefit) Recognized	(992)	(832)	(3,076)	(2,494)
FHTC [Member]
Investment Holdings [Line Items]
Equity method investment	22,403		22,403		16,815
Unfunded commitment, Equity	20,272		20,272		17,945
Amortization Expense	1,113	3,282	1,113	8,727
Tax Expense (Benefit) Recognized	(1,244)	(1,258)	(1,244)	(5,154)
CReED [Member]
Investment Holdings [Line Items]
Equity method investment					17
Unfunded commitment, Equity					538
Amortization Expense	13	687	13	687
Renewable Energy [Member]
Investment Holdings [Line Items]
Equity method investment	8,255		8,255		9,176
Unfunded commitment, Equity	4,951		4,951		$ 17,827
Amortization Expense	85	5,264	913	12,393
Tax Expense (Benefit) Recognized	$ (70)	$ (3,109)	$ (847)	$ (9,406)