Securities - Amortized Cost and Fair Value of Securities Available for Sale and Held to Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized cost within one year	$ 6,098	$ 3,643
Amortized cost one to five years	44,720	49,198
Amortized cost for five to ten years	16,147	106,225
Amortized cost for after ten years	6,598	62,120
Total amortized cost	73,563	221,186
Total available for sale investment securities, Amortized Cost	319,746	508,427
Within one year, amortized cost		9,910
One to five years, amortized cost	592
Five to ten years, amortized cost	99,225
After ten years, amortized cost	39,582
Total amortized cost	139,399	9,910
Total held to maturity investment securities, amortized cost	165,767us-gaap_HeldToMaturitySecurities	9,910us-gaap_HeldToMaturitySecurities
Fair value within one year	6,169	3,663
Fair value for one to five years	45,093	49,627
Fair value for five to ten years	16,768	107,424
Fair value for after ten years	6,790	61,051
Total fair value	74,820	221,765
Investment securities, available for sale	323,764us-gaap_AvailableForSaleSecurities	508,591us-gaap_AvailableForSaleSecurities
Within one year, fair value		9,910
One to five years, fair value	593
five to ten years, fair value	101,323
After ten years, fair value	40,857
Total fair value	142,773	9,910
Held-to-maturity, Fair Value	169,904	9,910
Federal Agency Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	122,930	116,047
Total held to maturity investment securities, amortized cost	4,039
Investment securities, available for sale	122,860	114,706
Held-to-maturity, Fair Value	4,073
Federal Agency Mortgage-backed Pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	122,583	170,006
Total held to maturity investment securities, amortized cost	22,329
Investment securities, available for sale	125,395	170,894
Held-to-maturity, Fair Value	23,058
Private Labeled Mortgage-backed Pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	670	1,188
Investment securities, available for sale	$ 689	$ 1,226

Available for sale securities debt maturities rolling fair value.

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Held To Maturity Securities Debt Maturities Amortized Cost

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Held To Maturity Securities Debt Maturities Fair Value Aggregate

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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 of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the next rolling twelve months following the latest balance sheet. 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. For 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 in the next rolling twelve months following the latest balance sheet. For 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 rolling twelve months following the latest balance sheet. 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. For 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 rolling twelve months following the latest balance sheet. For 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 sixth through tenth rolling twelve months following the latest balance sheet. 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. For 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 in the sixth through tenth rolling twelve months following the latest balance sheet. For 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 through fifth rolling twelve months following the latest balance sheet. 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. For 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 in the second through fifth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments, maturing in the fifth through tenth fiscal year following the latest fiscal year.

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Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments, maturing in the next fiscal year through the fifth fiscal year following the latest fiscal year.

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Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments, maturing after the tenth fiscal year following the latest fiscal year.

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Fair value of held-to-maturity debt securities maturing in the next rolling twelve months following the latest balance sheet. For 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 held-to-maturity debt securities maturing after the tenth rolling twelve months following the latest balance sheet. For 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 held-to-maturity debt securities maturing in the sixth through tenth rolling twelve months following the latest balance sheet. For 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 held-to-maturity debt securities maturing in the second through fifth rolling twelve months following the latest balance sheet. For 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 investments in debt securities classified as held-to-maturity.

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