Loans and Allowance for Credit Losses - Schedule of Activity in Troubled Debt Restructurings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable Impaired [Line Items]
Balance at beginning of period	$ 43,710	$ 54,003	$ 40,716
(Charge-offs)/recoveries	(4,010)	431	504
(Payments)/disbursements	(29,093)	(16,415)	(31,860)
Additions	21,131	5,691	44,643
Balance at end of period	31,738	43,710	54,003
Commercial Loan [Member]
Financing Receivable Impaired [Line Items]
Balance at beginning of period	10,275	12,088	16,802
(Charge-offs)/recoveries	(1,911)	(169)	417
(Payments)/disbursements	(3,733)	(5,188)	(18,519)
Additions	10,231	3,544	13,388
Balance at end of period	14,862	10,275	12,088
Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
Balance at beginning of period	27,671	34,705	18,327
(Charge-offs)/recoveries	(2,112)	561	381
(Payments)/disbursements	(23,182)	(8,808)	(11,752)
Additions	10,027	1,213	27,749
Balance at end of period	12,404	27,671	34,705
Residential [Member]
Financing Receivable Impaired [Line Items]
Balance at beginning of period	3,390	3,315	2,985
(Charge-offs)/recoveries		23
(Payments)/disbursements	(971)	(450)	(608)
Additions	557	502	938
Balance at end of period	2,976	3,390	3,315
Consumer Loan [Member]
Financing Receivable Impaired [Line Items]
Balance at beginning of period	2,374	3,895	2,602
(Charge-offs)/recoveries	13	16	(294)
(Payments)/disbursements	(1,207)	(1,969)	(981)
Additions	316	432	2,568
Balance at end of period	$ 1,496	$ 2,374	$ 3,895