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, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	6,074	5,091	$ 22,300
Impaired Originated & PNCI loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,690	2,480	21,498
Foreclosed assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,384	2,611	802
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	6,074	5,091	22,300
Level 3 [Member] | Impaired Originated & PNCI loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,690	2,480	21,498
Level 3 [Member] | Foreclosed assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,384	2,611	$ 802
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	(5.00%)	(5.00%)
Level 3 [Member] | Sales comparison approach [Member] | Minimum [Member] | Foreclosed assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	(5.00%)	(5.00%)
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	(41.00%)	(42.50%)
Level 3 [Member] | Sales comparison approach [Member] | Maximum [Member] | Foreclosed assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	(30.10%)	(29.40%)
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	(8.80%)	(10.10%)
Level 3 [Member] | Sales comparison approach [Member] | Weighted Average [Member] | Foreclosed assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustment for differences between comparable sales	(9.30%)	(8.20%)
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	8.00%	9.09%
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	9.10%	9.09%
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	8.10%	9.09%