Loans and Allowance for Credit Losses - Summary of Amortized Cost Balance of Financial Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	$ 16,910,790		$ 16,103,651
Related Allowance for Credit Losses	203,399	$ 205,773	218,583	$ 203,605	$ 191,146	$ 101,788
Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	57,890		87,731
Related Allowance for Credit Losses	3,931		10,127
Amortized Cost of Collateral Dependent Assets with no related Allowance	50,130		41,609
Commercial and Industrial Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	7,384,693		7,062,074
Related Allowance for Credit Losses	118,121	119,568	122,700	114,610	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	20,724		33,770
Related Allowance for Credit Losses	3,474		4,828
Amortized Cost of Collateral Dependent Assets with no related Allowance	17,250		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	7,229,696		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	18,790		29,684
Related Allowance for Credit Losses	3,474		4,828
Amortized Cost of Collateral Dependent Assets with no related Allowance	15,316		5,830
Commercial and Industrial Portfolio [Member] | Agriculture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	150,046		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	1,934		4,086
Amortized Cost of Collateral Dependent Assets with no related Allowance	1,934		4,086
Specialty Lending Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	482,398		511,300
Related Allowance for Credit Losses	5,901	4,673	5,219	929	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	16,999		19,436
Related Allowance for Credit Losses	415		4,663
Amortized Cost of Collateral Dependent Assets with no related Allowance	16,387		242
Specialty Lending Portfolio [Member] | Asset-based Lending [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	373,273		355,349
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	16,387		17,875
Related Allowance for Credit Losses			4,490
Amortized Cost of Collateral Dependent Assets with no related Allowance	16,387		242
Specialty Lending Portfolio [Member] | Factoring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	109,125		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	612		1,561
Related Allowance for Credit Losses	415		173
Commercial Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	6,246,368		5,908,934
Related Allowance for Credit Losses	56,734	60,043	61,931	55,834	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	15,262		28,587
Related Allowance for Credit Losses	42		582
Amortized Cost of Collateral Dependent Assets with no related Allowance	11,588		25,934
Commercial Real Estate Portfolio [Member] | Owner-occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	1,805,132		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	10,916		16,539
Related Allowance for Credit Losses	42
Amortized Cost of Collateral Dependent Assets with no related Allowance	7,242		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	2,771,193		2,472,535
Commercial Real Estate Portfolio [Member] | Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	489,930		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	943		8,625
Amortized Cost of Collateral Dependent Assets with no related Allowance	943		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	297,591		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	51,045		30,275
Commercial Real Estate Portfolio [Member] | General Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	831,477		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	3,403		3,423
Related Allowance for Credit Losses			582
Amortized Cost of Collateral Dependent Assets with no related Allowance	3,403		770
Consumer Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	2,138,796		1,945,494
Related Allowance for Credit Losses	5,807	4,183	6,586	5,952	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	4,813		5,850
Related Allowance for Credit Losses			54
Amortized Cost of Collateral Dependent Assets with no related Allowance	4,813		5,429
Consumer Real Estate Portfolio [Member] | HELOC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	358,389		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	2,764		3,170
Amortized Cost of Collateral Dependent Assets with no related Allowance	2,764		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	1,759,958		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	1,883		2,468
Related Allowance for Credit Losses			54
Amortized Cost of Collateral Dependent Assets with no related Allowance	1,883		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	20,449		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	166		212
Amortized Cost of Collateral Dependent Assets with no related Allowance	166		212
Consumer Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	110,330		117,986
Related Allowance for Credit Losses	857	603	1,480	1,606	1,127	543
Consumer Portfolio [Member] | Collateral Dependent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	92		88
Amortized Cost of Collateral Dependent Assets with no related Allowance	92		88
Consumer Portfolio [Member] | Revolving Line [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	57,287		65,215
Consumer Portfolio [Member] | Auto [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	27,513		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	58		69
Amortized Cost of Collateral Dependent Assets with no related Allowance	58		69
Consumer Portfolio [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	25,530		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	34		19
Amortized Cost of Collateral Dependent Assets with no related Allowance	34		19
Leases and Other Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	179,177		190,895
Related Allowance for Credit Losses	1,400	$ 1,600	2,271	$ 1,784	$ 2,308	$ 1,074
Leases and Other Portfolio [Member] | Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	2,363		2,413
Leases and Other Portfolio [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost of Collateral Dependent Assets	$ 176,814		$ 188,482