Fair Value Measurements - Assets and Liabilities at Fair Values (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	$ 964,534	$ 1,074,395
Foreclosed assets	10,546	5,098
Measured on A Recurring Basis[Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	964,534	1,074,395
Derivative assets	6,854	2,046
Assets, fair value disclosure	971,388	1,076,441
Derivative liabilities	6,745	2,052
Measured on A Recurring Basis[Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
Assets, fair value disclosure	0	0
Measured on A Recurring Basis[Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	873,681	970,779
Derivative assets	6,854	2,046
Assets, fair value disclosure	880,535	972,825
Derivative liabilities	6,745	2,052
Measured on A Recurring Basis[Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	90,853	103,616
Derivative assets	0
Assets, fair value disclosure	90,853	103,616
Measured on A Non-recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans measured for impairment based on the fair value of the underlying collateral	9,481	23,086
Foreclosed assets	10,546	5,098
Fair value assets, nonrecurring	20,027	28,184
Measured on A Non-recurring Basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans measured for impairment based on the fair value of the underlying collateral	9,481	23,086
Foreclosed assets	10,546	5,098
Fair value assets, nonrecurring	20,027	28,184
Measured on A Non-recurring Basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans measured for impairment based on the fair value of the underlying collateral	0	0
Foreclosed assets	0	0
Fair value assets, nonrecurring	0	0
Measured on A Non-recurring Basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans measured for impairment based on the fair value of the underlying collateral	0	0
Foreclosed assets	0	0
Fair value assets, nonrecurring	0	0
US Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	8,004	8,016
US Treasury Obligations [Member] | Measured on A Recurring Basis[Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	8,004	8,016
US Treasury Obligations [Member] | Measured on A Recurring Basis[Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
US Treasury Obligations [Member] | Measured on A Recurring Basis[Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
US Treasury Obligations [Member] | Measured on A Recurring Basis[Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	8,004	8,016
Agency Obligations [Member] | Measured on A Recurring Basis[Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	82,330	95,076
Agency Obligations [Member] | Measured on A Recurring Basis[Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
Agency Obligations [Member] | Measured on A Recurring Basis[Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
Agency Obligations [Member] | Measured on A Recurring Basis[Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	82,330	95,076
Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	863,861	957,257
Mortgage-Backed Securities [Member] | Measured on A Recurring Basis[Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	863,861	957,257
Mortgage-Backed Securities [Member] | Measured on A Recurring Basis[Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
Mortgage-Backed Securities [Member] | Measured on A Recurring Basis[Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	863,861	957,257
Mortgage-Backed Securities [Member] | Measured on A Recurring Basis[Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
State and Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	4,308	7,002
State and Municipal Obligations [Member] | Measured on A Recurring Basis[Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	4,308	7,002
State and Municipal Obligations [Member] | Measured on A Recurring Basis[Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
State and Municipal Obligations [Member] | Measured on A Recurring Basis[Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	4,308	7,002
State and Municipal Obligations [Member] | Measured on A Recurring Basis[Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
Corporate Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	5,512	6,520
Corporate Obligations [Member] | Measured on A Recurring Basis[Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	5,512	6,520
Corporate Obligations [Member] | Measured on A Recurring Basis[Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	5,512	6,520
Equities [Member] | Measured on A Recurring Basis[Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	519	524
Equities [Member] | Measured on A Recurring Basis[Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
Equities [Member] | Measured on A Recurring Basis[Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0	0
Equities [Member] | Measured on A Recurring Basis[Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	$ 519	$ 524