Loans and Allowance for Credit Losses - Summary of Amortized Cost Balance of Financial Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	$ 16,103,651
Related Allowance for Credit Losses	218,583	$ 101,788
Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	87,731
Related Allowance for Credit Losses	10,127
Amortized Cost of Collateral Dependent Assets with no related Allowance	41,609
Commercial and Industrial Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	7,062,074
Related Allowance for Credit Losses	122,700	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	33,770
Related Allowance for Credit Losses	4,828
Amortized Cost of Collateral Dependent Assets with no related Allowance	9,916
Commercial and Industrial Portfolio [Member] | Equipment/Accounts Receivable/Inventory [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	6,884,168
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	29,684
Related Allowance for Credit Losses	4,828
Amortized Cost of Collateral Dependent Assets with no related Allowance	5,830
Commercial and Industrial Portfolio [Member] | Agriculture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	161,581
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	4,086
Amortized Cost of Collateral Dependent Assets with no related Allowance	4,086
Specialty Lending Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	511,300
Related Allowance for Credit Losses	5,219	2,545
Specialty Lending Portfolio [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	19,436
Related Allowance for Credit Losses	4,663
Amortized Cost of Collateral Dependent Assets with no related Allowance	242
Specialty Lending Portfolio [Member] | Asset-based [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	355,349
Specialty Lending Portfolio [Member] | Asset-based [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	17,875
Related Allowance for Credit Losses	4,490
Amortized Cost of Collateral Dependent Assets with no related Allowance	242
Specialty Lending Portfolio [Member] | Factoring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	155,951
Specialty Lending Portfolio [Member] | Factoring [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	1,561
Related Allowance for Credit Losses	173
Commercial Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	5,908,934
Related Allowance for Credit Losses	61,931	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	28,587
Related Allowance for Credit Losses	582
Amortized Cost of Collateral Dependent Assets with no related Allowance	25,934
Commercial Real Estate Portfolio [Member] | Owner-occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	1,685,185
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	16,539
Amortized Cost of Collateral Dependent Assets with no related Allowance	16,539
Commercial Real Estate Portfolio [Member] | Non-owner-occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	2,472,535
Commercial Real Estate Portfolio [Member] | Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	502,463
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	8,625
Amortized Cost of Collateral Dependent Assets with no related Allowance	8,625
Commercial Real Estate Portfolio [Member] | 5+ Multi-family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	449,855
Commercial Real Estate Portfolio [Member] | 1-4 Family Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	30,275
Commercial Real Estate Portfolio [Member] | General Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	768,621
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	3,423
Related Allowance for Credit Losses	582
Amortized Cost of Collateral Dependent Assets with no related Allowance	770
Consumer Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	1,945,494
Related Allowance for Credit Losses	6,586	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	5,850
Related Allowance for Credit Losses	54
Amortized Cost of Collateral Dependent Assets with no related Allowance	5,429
Consumer Real Estate Portfolio [Member] | HELOC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	395,169
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	3,170
Amortized Cost of Collateral Dependent Assets with no related Allowance	3,170
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	1,528,494
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	2,468
Related Allowance for Credit Losses	54
Amortized Cost of Collateral Dependent Assets with no related Allowance	2,047
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	21,831
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	212
Amortized Cost of Collateral Dependent Assets with no related Allowance	212
Consumer Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	117,986
Related Allowance for Credit Losses	1,480	543
Consumer Portfolio [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	88
Amortized Cost of Collateral Dependent Assets with no related Allowance	88
Consumer Portfolio [Member] | Revolving Line [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	65,215
Consumer Portfolio [Member] | Auto [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	27,949
Consumer Portfolio [Member] | Auto [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
Consumer Portfolio [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	24,822
Consumer Portfolio [Member] | Other [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	19
Amortized Cost of Collateral Dependent Assets with no related Allowance	19
Leases and Other Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	190,895
Related Allowance for Credit Losses	2,271	$ 1,074
Leases and Other Portfolio [Member] | Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	2,413
Leases and Other Portfolio [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	$ 188,482