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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Investment Holdings [Line Items]
Total	$ 45,743		$ 45,743		$ 35,048
Total	27,785		27,785		20,816
Amortization Expense	940	$ 201	1,881	$ 402
Tax Benefit Recognized	(3,423)	(281)	(6,240)	(562)
LIHTC and Other Qualifying Investments [Member]
Investment Holdings [Line Items]
Proportional amortization method of investment	26,828		26,828		29,110
Unfunded commitment, Proportional amortization	14,692		14,692		16,210
Amortization Expense	940	201	1,881	402
Tax Benefit Recognized	(1,298)	$ (281)	(2,595)	$ (562)
FHTC [Member]
Investment Holdings [Line Items]
Equity method investment	17,411		17,411		4,434
Unfunded commitment, Equity	11,591		11,591		3,104
Tax Benefit Recognized	(1,519)		(3,039)
CReED [Member]
Investment Holdings [Line Items]
Equity method investment	1,504		1,504		1,504
Unfunded commitment, Equity	1,502		1,502		$ 1,502
Tax Benefit Recognized	$ (606)		$ (606)