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, 2015	Dec. 31, 2014
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	$ 2,327,355	$ 1,759,905
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	4,704	11,529
Impaired loans reserve	2,273	1,342
Not Designated as Hedging Instrument
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	9,295	7,552
Liabilities, recurring fair value measurements	13,932	9,716
Loans held for sale – fair value option
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	1,757,807	1,335,668
Impaired loans, net of reserves
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	4,346	2,380
Impaired loans reserve	2,273	1,342
Other real estate owned
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	358	9,149
Available-for-sale Securities | Mortgage-backed securities
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	500,974	377,311
Available-for-sale Securities | Corporate notes
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	40,067	15,104
Available-for-sale Securities | Equity securities
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	19,212	24,270
Quoted Prices in Active Markets for Identical Assets (Level 1)
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	19,212	24,270
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Not Designated as Hedging Instrument
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	0	0
Liabilities, recurring fair value measurements	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Loans held for sale – fair value option
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Impaired loans, net of reserves
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other real estate owned
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Available-for-sale Securities | Mortgage-backed securities
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Available-for-sale Securities | Corporate notes
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Available-for-sale Securities | Equity securities
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	19,212	24,270
Significant Other Observable Inputs (Level 2)
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	2,308,098	1,735,592
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	0	0
Significant Other Observable Inputs (Level 2) | Not Designated as Hedging Instrument
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	9,250	7,509
Liabilities, recurring fair value measurements	13,932	9,716
Significant Other Observable Inputs (Level 2) | Loans held for sale – fair value option
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	1,757,807	1,335,668
Significant Other Observable Inputs (Level 2) | Impaired loans, net of reserves
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	0	0
Significant Other Observable Inputs (Level 2) | Other real estate owned
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	0	0
Significant Other Observable Inputs (Level 2) | Available-for-sale Securities | Mortgage-backed securities
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	500,974	377,311
Significant Other Observable Inputs (Level 2) | Available-for-sale Securities | Corporate notes
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	40,067	15,104
Significant Other Observable Inputs (Level 2) | Available-for-sale Securities | Equity securities
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	0	0
Significant Unobservable Inputs (Level 3)
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	45	43
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	4,704	11,529
Significant Unobservable Inputs (Level 3) | Not Designated as Hedging Instrument
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	45	43
Liabilities, recurring fair value measurements	0	0
Significant Unobservable Inputs (Level 3) | Loans held for sale – fair value option
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	0	0
Significant Unobservable Inputs (Level 3) | Impaired loans, net of reserves
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	4,346	2,380
Significant Unobservable Inputs (Level 3) | Other real estate owned
Measured at Fair Value on a Nonrecurring Basis:
Assets, nonrecurring fair value measurements	358	9,149
Significant Unobservable Inputs (Level 3) | Available-for-sale Securities | Mortgage-backed securities
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	0	0
Significant Unobservable Inputs (Level 3) | Available-for-sale Securities | Corporate notes
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	0	0
Significant Unobservable Inputs (Level 3) | Available-for-sale Securities | Equity securities
Measured at Fair Value on a Recurring Basis:
Assets, recurring fair value measurements	$ 0	$ 0