Disclosures About Fair Value of Financial Instruments - Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring and Nonrecurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Assets
Fair Value	$ 2,746,728	$ 2,961,015
Fair Value, Measurements, Recurring
Assets
Assets, fair value	3,763,289	4,329,084
Fair Value, Measurements, Nonrecurring
Assets
Assets, fair value	3,515	4,819
Asset-backed securities
Assets
Fair Value	104,716	160,542
Asset-backed securities | Fair Value, Measurements, Recurring
Assets
Fair Value	104,716	160,542
Agency-guaranteed residential collateralized mortgage obligations
Assets
Fair Value	118,469	133,864
Agency-guaranteed residential collateralized mortgage obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	118,469	133,864
Collateralized loan obligations
Assets
Fair Value	815,856	872,738
Collateralized loan obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	815,856	872,738
Commercial mortgage-backed securities
Assets
Fair Value	131,188	136,357
Commercial mortgage-backed securities | Fair Value, Measurements, Recurring
Assets
Fair Value	131,188	136,357
Corporate notes
Assets
Fair Value	578,897	595,253
Corporate notes | Fair Value, Measurements, Recurring
Assets
Fair Value	578,897	595,253
Private label collateralized mortgage obligations
Assets
Fair Value	997,602	1,062,261
Private label collateralized mortgage obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	997,602	1,062,261
Derivatives | Fair Value, Measurements, Recurring
Assets
Assets, fair value	28,475	44,435
Loans held for sale – fair value option | Fair Value, Measurements, Recurring
Assets
Assets, fair value	25,520	322
Loans receivable, mortgage warehouse – fair value option | Fair Value, Measurements, Recurring
Assets
Assets, fair value	962,566	1,323,312
Derivatives  | Fair Value, Measurements, Recurring
Liabilities
Financial liabilities, fair value	41,433	42,106
Collateral-dependent loans | Fair Value, Measurements, Nonrecurring
Assets
Assets, fair value	3,515	4,819
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Assets
Assets, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Nonrecurring
Assets
Assets, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed securities | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Agency-guaranteed residential collateralized mortgage obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Collateralized loan obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial mortgage-backed securities | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate notes | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Private label collateralized mortgage obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives | Fair Value, Measurements, Recurring
Assets
Assets, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Loans held for sale – fair value option | Fair Value, Measurements, Recurring
Assets
Assets, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Loans receivable, mortgage warehouse – fair value option | Fair Value, Measurements, Recurring
Assets
Assets, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives  | Fair Value, Measurements, Recurring
Liabilities
Financial liabilities, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Collateral-dependent loans | Fair Value, Measurements, Nonrecurring
Assets
Assets, fair value	0	0
Significant Other Observable Inputs (Level 2)
Assets
Fair Value	2,704,363	2,887,749
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets
Assets, fair value	3,696,355	4,255,763
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Nonrecurring
Assets
Assets, fair value	0	0
Significant Other Observable Inputs (Level 2) | Asset-backed securities | Fair Value, Measurements, Recurring
Assets
Fair Value	62,351	87,276
Significant Other Observable Inputs (Level 2) | Agency-guaranteed residential collateralized mortgage obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	118,469	133,864
Significant Other Observable Inputs (Level 2) | Collateralized loan obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	815,856	872,738
Significant Other Observable Inputs (Level 2) | Commercial mortgage-backed securities | Fair Value, Measurements, Recurring
Assets
Fair Value	131,188	136,357
Significant Other Observable Inputs (Level 2) | Corporate notes | Fair Value, Measurements, Recurring
Assets
Fair Value	578,897	595,253
Significant Other Observable Inputs (Level 2) | Private label collateralized mortgage obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	997,602	1,062,261
Significant Other Observable Inputs (Level 2) | Derivatives | Fair Value, Measurements, Recurring
Assets
Assets, fair value	28,421	44,380
Significant Other Observable Inputs (Level 2) | Loans held for sale – fair value option | Fair Value, Measurements, Recurring
Assets
Assets, fair value	1,005	322
Significant Other Observable Inputs (Level 2) | Loans receivable, mortgage warehouse – fair value option | Fair Value, Measurements, Recurring
Assets
Assets, fair value	962,566	1,323,312
Significant Other Observable Inputs (Level 2) | Derivatives  | Fair Value, Measurements, Recurring
Liabilities
Financial liabilities, fair value	41,433	42,106
Significant Other Observable Inputs (Level 2) | Collateral-dependent loans | Fair Value, Measurements, Nonrecurring
Assets
Assets, fair value	0	0
Significant Unobservable Inputs (Level 3)
Assets
Fair Value	42,365	73,266
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Assets
Assets, fair value	66,934	73,321
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Nonrecurring
Assets
Assets, fair value	3,515	4,819
Significant Unobservable Inputs (Level 3) | Asset-backed securities
Assets
Fair Value	42,365	73,266
Significant Unobservable Inputs (Level 3) | Asset-backed securities | Fair Value, Measurements, Recurring
Assets
Fair Value	42,365	73,266
Significant Unobservable Inputs (Level 3) | Agency-guaranteed residential collateralized mortgage obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Collateralized loan obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Commercial mortgage-backed securities | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Corporate notes | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Private label collateralized mortgage obligations | Fair Value, Measurements, Recurring
Assets
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Derivatives | Fair Value, Measurements, Recurring
Assets
Assets, fair value	54	55
Significant Unobservable Inputs (Level 3) | Loans held for sale – fair value option | Fair Value, Measurements, Recurring
Assets
Assets, fair value	24,515	0
Significant Unobservable Inputs (Level 3) | Loans receivable, mortgage warehouse – fair value option | Fair Value, Measurements, Recurring
Assets
Assets, fair value	0	0
Significant Unobservable Inputs (Level 3) | Derivatives  | Fair Value, Measurements, Recurring
Liabilities
Financial liabilities, fair value	0	0
Significant Unobservable Inputs (Level 3) | Collateral-dependent loans | Fair Value, Measurements, Nonrecurring
Assets
Assets, fair value	$ 3,515	$ 4,819