Disclosures about Fair Value of Financial Instruments - Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring and Non-recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets
Impaired loans reserve	$ 852	$ 845
Impaired loans, net of reserves
Assets
Impaired loans reserve	852	845
Fair Value, Measurements, Recurring
Assets
Assets	2,867,372	2,086,632
Fair Value, Measurements, Recurring | Interest-only GNMA securities
Assets
Assets	16,272
Fair Value, Measurements, Recurring | Equity securities
Assets
Assets	2,406	1,718
Fair Value, Measurements, Recurring | Derivatives
Assets
Assets	23,608	14,693
Liabilities
Liabilities	45,939	16,286
Fair Value, Measurements, Recurring | Loans held for sale – fair value option
Assets
Assets	2,130	1,507
Fair Value, Measurements, Recurring | Loans receivable, mortgage warehouse – fair value option
Assets
Assets	2,245,758	1,405,420
Fair Value, Measurements, Recurring | Available-for-sale Securities | Agency-guaranteed residential mortgage-backed securities
Assets
Assets	278,321	305,374
Fair Value, Measurements, Recurring | Available-for-sale Securities | Corporate notes
Assets
Assets	298,877	357,920
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Assets	2,406	1,718
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest-only GNMA securities
Assets
Assets	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
Assets
Assets	2,406	1,718
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives
Assets
Assets	0	0
Liabilities
Liabilities	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Loans held for sale – fair value option
Assets
Assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Loans receivable, mortgage warehouse – fair value option
Assets
Assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Available-for-sale Securities | Agency-guaranteed residential mortgage-backed securities
Assets
Assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Available-for-sale Securities | Corporate notes
Assets
Assets	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets
Assets	2,848,615	2,084,845
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest-only GNMA securities
Assets
Assets	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Equity securities
Assets
Assets	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Derivatives
Assets
Assets	23,529	14,624
Liabilities
Liabilities	45,939	16,286
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Loans held for sale – fair value option
Assets
Assets	2,130	1,507
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Loans receivable, mortgage warehouse – fair value option
Assets
Assets	2,245,758	1,405,420
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Available-for-sale Securities | Agency-guaranteed residential mortgage-backed securities
Assets
Assets	278,321	305,374
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Available-for-sale Securities | Corporate notes
Assets
Assets	298,877	357,920
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets
Assets	16,351	69
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Interest-only GNMA securities
Assets
Assets	16,272
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Equity securities
Assets
Assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Derivatives
Assets
Assets	79	69
Liabilities
Liabilities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Loans held for sale – fair value option
Assets
Assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Loans receivable, mortgage warehouse – fair value option
Assets
Assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Available-for-sale Securities | Agency-guaranteed residential mortgage-backed securities
Assets
Assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Available-for-sale Securities | Corporate notes
Assets
Assets	0	0
Fair Value, Measurements, Nonrecurring
Assets
Assets	14,350	11,497
Fair Value, Measurements, Nonrecurring | Impaired loans, net of reserves
Assets
Assets	14,272	10,876
Fair Value, Measurements, Nonrecurring | Other real estate owned
Assets
Assets	78	621
Fair Value, Measurements, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Assets	0	0
Fair Value, Measurements, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Impaired loans, net of reserves
Assets
Assets	0	0
Fair Value, Measurements, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other real estate owned
Assets
Assets	0	0
Fair Value, Measurements, Nonrecurring | Significant Other Observable Inputs (Level 2)
Assets
Assets	0	0
Fair Value, Measurements, Nonrecurring | Significant Other Observable Inputs (Level 2) | Impaired loans, net of reserves
Assets
Assets	0	0
Fair Value, Measurements, Nonrecurring | Significant Other Observable Inputs (Level 2) | Other real estate owned
Assets
Assets	0	0
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3)
Assets
Assets	14,350	11,497
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Impaired loans, net of reserves
Assets
Assets	14,272	10,876
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Other real estate owned
Assets
Assets	$ 78	$ 621