Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Unrealized losses on available-for-sale securities	$ 0	$ 4,350
Allowance for loan and lease losses	9,991	8,303
Purchase accounting adjustments—loans	32,333	2,427
Reserves and other accruals	14,663	10,426
Investments	2,323	0
Deferred gains	465	458
Net operating losses	142	165
Derivatives	182	775
Employee benefit plans	3,581	0
Lease liabilities	38,181	0
Reverse mortgages	26	384
Total deferred tax assets	101,887	27,288
Deferred tax liabilities:
Unrealized gains on available-for-sale securities	(8,651)	0
Unrealized gains on equity investments	(10,031)	(4,203)
Accelerated depreciation	(1,745)	(806)
Other	(841)	(537)
Right of use assets	(34,907)	0
Deferred loan costs	(2,843)	(2,052)
Intangibles	(24,625)	(4,130)
Total deferred tax liabilities	(83,643)	(11,728)
Net deferred tax asset	$ 18,244	$ 15,560