Loans - Summary of Recorded Investment in Non-accrual Loans and Loans Past Due Over 90 Days Still on Accrual by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable Recorded Investment Past Due [Line Items]
Loans past due over 90 days still accruing	$ 535	$ 1,692
Non-PCD Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	38,776
Non-accrual with allocated allowance for credit losses	6,529
Loans past due over 90 days still accruing	535	1,692
Non-accrual	45,305	36,916
Non-PCD Loans [Member] | Residential Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	11,537
Non-accrual with allocated allowance for credit losses	926
Non-accrual	12,463	13,455
Non-PCD Loans [Member] | Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	18,386
Non-accrual with allocated allowance for credit losses	2,264
Non-accrual	20,650	12,141
Non-PCD Loans [Member] | Land, Development, Construction [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	2,107
Non-accrual with allocated allowance for credit losses	470
Non-accrual		2,516
Non-PCD Loans [Member] | Consumer and Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	1,033
Non-accrual	1,033	920
Non-PCD Loans [Member] | Commercial and Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	5,713
Non-accrual with allocated allowance for credit losses	2,869
Loans past due over 90 days still accruing	535	1,692
Non-accrual		$ 7,884
PCD Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	22,315
Non-accrual with allocated allowance for credit losses	11,578
Non-accrual	33,893
PCD Loans [Member] | Residential Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	8,847
Non-accrual	8,847
PCD Loans [Member] | Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	10,722
Non-accrual with allocated allowance for credit losses	9,609
Non-accrual	20,331
PCD Loans [Member] | Land, Development, Construction [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	1,334
PCD Loans [Member] | Consumer and Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	16
Non-accrual	16
PCD Loans [Member] | Commercial and Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual with no allocated allowance for credit losses	1,396
Non-accrual with allocated allowance for credit losses	$ 1,969