Loans - Summary of Allowance for Loan Losses and Recorded Investment in Loans by Portfolios (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 40,655	$ 39,770
Impact of adopting ASC 326	74,608
Loans charged-off	(3,607)	(1,447)
Recoveries of loans previously charged-off	2,163	676
Net (charge-offs) recoveries	(1,444)	(771)
Provision for credit losses	44,914	1,053
Balance at end of period	158,733	40,052
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,257
Balance at end of period	23,083
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	18,552
Balance at end of period	103,629
Land, Development, Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	2,496
Balance at end of period	14,439
Commercial Industrial and Factored Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	11,282
Balance at end of period	13,649
Consumer and Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,068
Balance at end of period	3,933
Allowance for loan losses for loans that are not PCI loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	40,429	39,579
Impact of adopting ASC 326	57,604
Loans charged-off	(2,350)	(1,447)
Recoveries of loans previously charged-off	1,201	676
Net (charge-offs) recoveries	(1,149)	(771)
Provision for credit losses	43,919	1,053
Balance at end of period	140,803	39,861
PCD [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	226	191
Impact of adopting ASC 326	17,004
Loans charged-off	(1,257)
Recoveries of loans previously charged-off	962
Net (charge-offs) recoveries	(295)
Provision for credit losses	995
Balance at end of period	17,930	191
PCD [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impact of adopting ASC 326	3,021
Loans charged-off	(156)
Recoveries of loans previously charged-off	141
Provision for credit losses	(154)
Balance at end of period	2,852
PCD [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impact of adopting ASC 326	11,966
Loans charged-off	(1,021)
Recoveries of loans previously charged-off	244
Provision for credit losses	914
Balance at end of period	12,103
PCD [Member] | Land, Development, Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	177	177
Impact of adopting ASC 326	79
Recoveries of loans previously charged-off	293
Provision for credit losses	(291)
Balance at end of period	258	177
PCD [Member] | Commercial Industrial and Factored Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impact of adopting ASC 326	1,924
Loans charged-off	(80)
Recoveries of loans previously charged-off	283
Provision for credit losses	533
Balance at end of period	2,660
PCD [Member] | Consumer and Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	49	14
Impact of adopting ASC 326	14
Recoveries of loans previously charged-off	1
Provision for credit losses	(7)
Balance at end of period	57	14
Allowance for loan losses for loans that are not PCD loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	40,429	39,579
Impact of adopting ASC 326	57,604
Loans charged-off	(2,350)	(1,447)
Recoveries of loans previously charged-off	1,201	676
Provision for credit losses	43,919	1,053
Balance at end of period	140,803	39,861
Allowance for loan losses for loans that are not PCD loans [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,257	5,518
Impact of adopting ASC 326	11,412
Loans charged-off	(294)	(201)
Recoveries of loans previously charged-off	181	142
Provision for credit losses	4,675	(11)
Balance at end of period	20,231	5,448
Allowance for loan losses for loans that are not PCD loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	18,552	22,978
Impact of adopting ASC 326	35,596
Recoveries of loans previously charged-off	305	152
Provision for credit losses	37,073	(883)
Balance at end of period	91,526	22,247
Allowance for loan losses for loans that are not PCD loans [Member] | Land, Development, Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	2,319	1,781
Impact of adopting ASC 326	6,932
Loans charged-off	(24)	(31)
Recoveries of loans previously charged-off	25	83
Provision for credit losses	4,929	387
Balance at end of period	14,181	2,220
Allowance for loan losses for loans that are not PCD loans [Member] | Commercial Industrial and Factored Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	11,282	6,414
Impact of adopting ASC 326	2,995
Loans charged-off	(1,117)	(664)
Recoveries of loans previously charged-off	556	155
Provision for credit losses	(2,727)	1,025
Balance at end of period	10,989	6,930
Allowance for loan losses for loans that are not PCD loans [Member] | Consumer and Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,019	2,888
Impact of adopting ASC 326	669
Loans charged-off	(915)	(551)
Recoveries of loans previously charged-off	134	144
Provision for credit losses	(31)	535
Balance at end of period	$ 3,876	$ 3,016