Securities - Maturities of Debt Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized cost of debt securities available for sale, due within one year	$ 4,579
Amortized cost of debt securities available for sale, due in one to five years	13,932	$ 17,939
Amortized cost of debt securities available for sale, due in five to ten years	32,998	42,151
Amortized cost of debt securities available for sale, due after ten years	14,052	22,702
Total amortized cost debt securities available for sale with specific maturities	65,561	82,792
Amortized Cost	207,255	233,429
Estimated fair value of debt securities available for sale, due within one year	4,590
Estimated fair value of debt securities available for sale, due in one to five years	14,287	18,304
Estimated fair value of debt securities available for sale, due in five to ten years	34,297	42,793
Estimated fair value of debt securities available for sale, due after ten years	15,211	24,088
Total estimated fair value of debt securities available for sale with specific maturities	68,385	85,185
Total securities available for sale at estimated fair value	213,289	237,177
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost of debt securities available for sale without specific maturities	85,898	89,690
Total estimated fair value of debt securities available for sale without specific maturities	87,012	89,543
Amortizing Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost of debt securities available for sale without specific maturities	55,796	60,947
Total estimated fair value of debt securities available for sale without specific maturities	$ 57,892	$ 62,449

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing after the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing after the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of investment in available-for-sale debt securities with a single maturity date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the next fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of available-for-sale debt securities at cost, net of adjustments, that do not have a single maturity date and which the entity has decided to disclose separately rather than allocating the cost over several maturity groupings. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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