Investment Securities - Summary of Continuous Loss Position of Securities (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Investment [Line Items]
Fair Value, Less than 12 months	$ 194,146,000	$ 233,909,000
Gross Unrealized Holding Losses, Less than 12 months	1,109,000	1,206,000
Fair Value, 12 months or longer	70,017,000
Gross unrealized holding losses, 12 months or longer	859,000
Fair Value	264,163,000	233,909,000
Gross Unrealized Holding Losses	1,968,000	1,206,000
Gross unrealized holding losses	0
CMO [Member]
Investment [Line Items]
Fair Value, Less than 12 months		2,383,000
Gross Unrealized Holding Losses, Less than 12 months
Fair Value, 12 months or longer
Gross unrealized holding losses, 12 months or longer
Fair Value		2,383,000
Gross unrealized holding losses
Government agency [Member]
Investment [Line Items]
Fair Value, Less than 12 months	51,134,000
Gross Unrealized Holding Losses, Less than 12 months	248,000
Fair Value, 12 months or longer
Gross unrealized holding losses, 12 months or longer
Fair Value	51,134,000
Gross Unrealized Holding Losses	248,000
Residential Mortgage-Backed Securities [Member]
Investment [Line Items]
Fair Value, Less than 12 months	55,118,000	75,754,000
Gross Unrealized Holding Losses, Less than 12 months	127,000	334,000
Fair Value, 12 months or longer
Gross unrealized holding losses, 12 months or longer
Fair Value	55,118,000	75,754,000
Gross Unrealized Holding Losses	127,000	334,000
CMO's / REMIC's-residential [Member]
Investment [Line Items]
Fair Value, Less than 12 months	74,784,000	133,471,000
Gross Unrealized Holding Losses, Less than 12 months	572,000	665,000
Fair Value, 12 months or longer	69,042,000
Gross unrealized holding losses, 12 months or longer	838,000
Fair Value	143,826,000	133,471,000
Gross Unrealized Holding Losses	1,410,000	665,000
Municipal bonds [Member]
Investment [Line Items]
Fair Value, Less than 12 months	13,110,000	22,184,000
Gross Unrealized Holding Losses, Less than 12 months	162,000	203,000
Fair Value, 12 months or longer	975,000
Gross unrealized holding losses, 12 months or longer	21,000
Fair Value	14,085,000	22,184,000
Gross Unrealized Holding Losses	183,000	203,000
Other Securities [Member]
Investment [Line Items]
Fair Value, Less than 12 months		2,500,000
Gross Unrealized Holding Losses, Less than 12 months		4,000
Fair Value, 12 months or longer
Gross unrealized holding losses, 12 months or longer
Fair Value		2,500,000
Gross Unrealized Holding Losses		$ 4,000

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Amount of the excess of amortized cost basis over fair value of securities that have been in a loss position for twelve months or longer for securities which are categorized neither as held-to-maturity nor trading securities.

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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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