Loans and Allowance for Credit Losses - Summary of Amortized Cost Balance of Financial Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	$ 13,949,710
Related Allowance for Credit Losses	191,146	$ 101,788
Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	96,609
Related Allowance for Credit Losses	7,345
Amortized Cost of Collateral Dependent Assets with no related Allowance	67,677
Commercial and Industrial Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	5,952,364
Related Allowance for Credit Losses	122,532	63,313
Commercial and Industrial Portfolio [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	42,613
Related Allowance for Credit Losses	6,607
Amortized Cost of Collateral Dependent Assets with no related Allowance	22,102
Commercial and Industrial Portfolio [Member] | Equipment/Accounts Receivable/Inventory [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	5,758,200
Commercial and Industrial Portfolio [Member] | Equipment/Accounts Receivable/Inventory [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	34,636
Related Allowance for Credit Losses	6,607
Amortized Cost of Collateral Dependent Assets with no related Allowance	14,125
Commercial and Industrial Portfolio [Member] | Agriculture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	178,562
Commercial and Industrial Portfolio [Member] | Agriculture [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	7,977
Amortized Cost of Collateral Dependent Assets with no related Allowance	7,977
Specialty Lending Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	523,425
Related Allowance for Credit Losses	3,549	2,545
Specialty Lending Portfolio [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	1,455
Related Allowance for Credit Losses	41
Amortized Cost of Collateral Dependent Assets with no related Allowance	1,011
Specialty Lending Portfolio [Member] | Asset-based Lending [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	356,636
Specialty Lending Portfolio [Member] | Asset-based Lending [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	907
Amortized Cost of Collateral Dependent Assets with no related Allowance	907
Specialty Lending Portfolio [Member] | Factoring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	166,789
Specialty Lending Portfolio [Member] | Factoring [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	548
Related Allowance for Credit Losses	41
Amortized Cost of Collateral Dependent Assets with no related Allowance	104
Commercial Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	5,283,787
Related Allowance for Credit Losses	35,395	15,951
Commercial Real Estate Portfolio [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	46,587
Related Allowance for Credit Losses	616
Amortized Cost of Collateral Dependent Assets with no related Allowance	38,703
Commercial Real Estate Portfolio [Member] | Owner-occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	1,567,358
Commercial Real Estate Portfolio [Member] | Owner-occupied [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	32,561
Related Allowance for Credit Losses	21
Amortized Cost of Collateral Dependent Assets with no related Allowance	27,389
Commercial Real Estate Portfolio [Member] | Non-owner-occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	1,921,143
Commercial Real Estate Portfolio [Member] | Non-owner-occupied [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	1,221
Amortized Cost of Collateral Dependent Assets with no related Allowance	1,221
Commercial Real Estate Portfolio [Member] | Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	426,756
Commercial Real Estate Portfolio [Member] | Farmland [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	9,316
Amortized Cost of Collateral Dependent Assets with no related Allowance	9,316
Commercial Real Estate Portfolio [Member] | 5+ Multi-family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	390,716
Commercial Real Estate Portfolio [Member] | 1-4 Family Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	40,463
Commercial Real Estate Portfolio [Member] | General Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	937,351
Commercial Real Estate Portfolio [Member] | General Construction [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	3,489
Related Allowance for Credit Losses	595
Amortized Cost of Collateral Dependent Assets with no related Allowance	777
Consumer Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	1,444,511
Related Allowance for Credit Losses	4,177	2,623
Consumer Real Estate Portfolio [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	5,701
Related Allowance for Credit Losses	81
Amortized Cost of Collateral Dependent Assets with no related Allowance	5,608
Consumer Real Estate Portfolio [Member] | HELOC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	477,187
Consumer Real Estate Portfolio [Member] | HELOC [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	3,351
Amortized Cost of Collateral Dependent Assets with no related Allowance	3,351
Consumer Real Estate Portfolio [Member] | First Lien: 1-4 Family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	946,039
Consumer Real Estate Portfolio [Member] | First Lien: 1-4 Family [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	2,082
Amortized Cost of Collateral Dependent Assets with no related Allowance	2,082
Consumer Real Estate Portfolio [Member] | Junior Lien: 1-4 Family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	21,285
Consumer Real Estate Portfolio [Member] | Junior Lien: 1-4 Family [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	268
Related Allowance for Credit Losses	81
Amortized Cost of Collateral Dependent Assets with no related Allowance	175
Consumer Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	146,721
Related Allowance for Credit Losses	1,127	543
Consumer Portfolio [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	184
Amortized Cost of Collateral Dependent Assets with no related Allowance	184
Consumer Portfolio [Member] | Revolving Line [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	86,012
Consumer Portfolio [Member] | Revolving Line [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	124
Amortized Cost of Collateral Dependent Assets with no related Allowance	124
Consumer Portfolio [Member] | Auto [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	28,800
Consumer Portfolio [Member] | Auto [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	56
Amortized Cost of Collateral Dependent Assets with no related Allowance	56
Consumer Portfolio [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	31,909
Consumer Portfolio [Member] | Other [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	4
Amortized Cost of Collateral Dependent Assets with no related Allowance	4
Leases and Other Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	225,295
Related Allowance for Credit Losses	2,308	$ 1,074
Leases and Other Portfolio [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	69
Amortized Cost of Collateral Dependent Assets with no related Allowance	69
Leases and Other Portfolio [Member] | Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	2,159
Leases and Other Portfolio [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	223,136
Leases and Other Portfolio [Member] | Other [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	69
Amortized Cost of Collateral Dependent Assets with no related Allowance	$ 69