Loans and Allowance for Credit Losses - Schedule of Activity in Troubled Debt Restructurings (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Roll Forward]
Beginning Balance	$ 31,738	$ 43,710
(Charge-offs)/ Recoveries	1,961	(85)
(Payments)/ Disbursements	(1,103)	(2,792)
Additions	0	5,510
Ending Balance	28,674	46,343
Commercial
Financing Receivable, Troubled Debt Restructuring [Roll Forward]
Beginning Balance	12,412	10,275
(Charge-offs)/ Recoveries	695	(7)
(Payments)/ Disbursements	(789)	(1,029)
Additions	0	2,407
Ending Balance	10,928	11,646
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Roll Forward]
Beginning Balance	14,277	27,671
(Charge-offs)/ Recoveries	1,272	(75)
(Payments)/ Disbursements	(157)	(1,562)
Additions	0	3,103
Ending Balance	12,848	29,137
BBCC
Financing Receivable, Troubled Debt Restructuring [Roll Forward]
Beginning Balance	578
(Charge-offs)/ Recoveries	0
(Payments)/ Disbursements	(16)
Additions	0
Ending Balance	562
Residential real estate
Financing Receivable, Troubled Debt Restructuring [Roll Forward]
Beginning Balance	3,107	3,390
(Charge-offs)/ Recoveries	0	0
(Payments)/ Disbursements	(67)	(143)
Additions	0	0
Ending Balance	3,040	3,247
Indirect
Financing Receivable, Troubled Debt Restructuring [Roll Forward]
Beginning Balance	0
(Charge-offs)/ Recoveries	(3)
(Payments)/ Disbursements	(3)
Additions	0
Ending Balance	0
Direct
Financing Receivable, Troubled Debt Restructuring [Roll Forward]
Beginning Balance	983
(Charge-offs)/ Recoveries	(2)
(Payments)/ Disbursements	(63)
Additions	0
Ending Balance	922
Home equity
Financing Receivable, Troubled Debt Restructuring [Roll Forward]
Beginning Balance	381
(Charge-offs)/ Recoveries	(1)
(Payments)/ Disbursements	(8)
Additions	0
Ending Balance	$ 374
Consumer
Financing Receivable, Troubled Debt Restructuring [Roll Forward]
Beginning Balance		2,374
(Charge-offs)/ Recoveries		(3)
(Payments)/ Disbursements		(58)
Additions		0
Ending Balance		$ 2,313