Fair Value Measurement - Quantitative Information about Level 3 Fair Value Measurements for Financial Instruments Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Impaired Originated & PNCI Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 824	$ 1,107
Foreclosed Assets [Member] | Land & Construction [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		15
Foreclosed Assets [Member] | Residential Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 657	1,564
Foreclosed Assets [Member] | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		$ 674
Level 3 [Member] | Sales Comparison Approach [Member] | Minimum [Member] | Impaired Originated & PNCI Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	(20.70%)
Level 3 [Member] | Sales Comparison Approach [Member] | Minimum [Member] | Foreclosed Assets [Member] | Residential Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	(22.60%)
Level 3 [Member] | Sales Comparison Approach [Member] | Minimum [Member] | Foreclosed Assets [Member] | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	(65.00%)
Level 3 [Member] | Sales Comparison Approach [Member] | Maximum [Member] | Impaired Originated & PNCI Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	46.30%
Level 3 [Member] | Sales Comparison Approach [Member] | Maximum [Member] | Foreclosed Assets [Member] | Residential Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	14.30%
Level 3 [Member] | Sales Comparison Approach [Member] | Maximum [Member] | Foreclosed Assets [Member] | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	62.50%
Level 3 [Member] | Sales Comparison Approach [Member] | Weighted Average [Member] | Impaired Originated & PNCI Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	1.90%
Level 3 [Member] | Sales Comparison Approach [Member] | Weighted Average [Member] | Foreclosed Assets [Member] | Residential Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	0.10%
Level 3 [Member] | Sales Comparison Approach [Member] | Weighted Average [Member] | Foreclosed Assets [Member] | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	(6.90%)
Level 3 [Member] | Income Approach [Member] | Minimum [Member] | Impaired Originated & PNCI Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Capitalization rate	0.00%
Level 3 [Member] | Income Approach [Member] | Maximum [Member] | Impaired Originated & PNCI Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Capitalization rate	0.00%
Level 3 [Member] | Income Approach [Member] | Weighted Average [Member] | Impaired Originated & PNCI Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Capitalization rate	0.00%