Fair Value Disclosures of Financial Assets and Liabilities - Schedule of Financial Instruments Carried at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	$ 810,433	$ 794,543
Total assets measured at fair value on a recurring basis	811,771	796,051
Other real estate owned	3,924	3,591
Loans held for sale	19,313	54,782
Impaired loans, net	52,903	46,499
Total assets measured at fair value on a nonrecurring basis	76,140	104,872
Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Other liabilities	2,736	3,380
GSE | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale		35,010
CMO
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	267,808	261,216
CMO | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	267,808	261,215
FNMA MBS
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	431,242	405,764
FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	431,242	405,764
FHLMC MBS
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	85,062	63,514
FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	85,062	63,515
GNMA MBS
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	25,697	28,416
GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	25,697	28,416
Other investments | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	624	623
Other assets | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	1,338	1,508
Quoted Prices in Active Markets for Identical Asset (Level 1)
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets measured at fair value on a recurring basis	624	623
Other real estate owned	0	0
Loans held for sale	0	0
Impaired loans, net	0	0
Total assets measured at fair value on a nonrecurring basis	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Other liabilities	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | GSE | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale		0
Quoted Prices in Active Markets for Identical Asset (Level 1) | CMO | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Other investments | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	624	623
Quoted Prices in Active Markets for Identical Asset (Level 1) | Other assets | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Significant Other Observable Inputs (Level 2)
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets measured at fair value on a recurring basis	811,147	795,428
Other real estate owned	0	0
Loans held for sale	19,313	54,782
Impaired loans, net	0	0
Total assets measured at fair value on a nonrecurring basis	19,313	54,782
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Other liabilities	2,736	3,380
Significant Other Observable Inputs (Level 2) | GSE | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale		35,010
Significant Other Observable Inputs (Level 2) | CMO | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	267,808	261,215
Significant Other Observable Inputs (Level 2) | FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	431,242	405,764
Significant Other Observable Inputs (Level 2) | FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	85,062	63,515
Significant Other Observable Inputs (Level 2) | GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	25,697	28,416
Significant Other Observable Inputs (Level 2) | Other investments | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Significant Other Observable Inputs (Level 2) | Other assets | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	1,338	1,508
Significant Unobservable Inputs (Level 3)
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets measured at fair value on a recurring basis	0	0
Other real estate owned	3,924	3,591
Loans held for sale	0	0
Impaired loans, net	52,903	46,499
Total assets measured at fair value on a nonrecurring basis	56,827	50,090
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Other liabilities	0	0
Significant Unobservable Inputs (Level 3) | GSE | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale		0
Significant Unobservable Inputs (Level 3) | CMO | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Significant Unobservable Inputs (Level 3) | FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Significant Unobservable Inputs (Level 3) | FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Significant Unobservable Inputs (Level 3) | GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Significant Unobservable Inputs (Level 3) | Other investments | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Significant Unobservable Inputs (Level 3) | Other assets | Fair Value, Measurements, Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Investment securities available for sale	$ 0	$ 0