Gross Amortized Cost and Fair Value of Securities Available for Sale and Related Gross Unrealized Gains and Losses Recognized in Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	$ 413,023	$ 429,611
Gross Unrealized Gains	8,830	8,771
Gross Unrealized Losses	(410)	(136)
Fair Value	421,443	438,246
U.S. Treasury securities and U.S. Government agencies
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	38,954	38,931
Gross Unrealized Gains	454	547
Gross Unrealized Losses	(4)	(6)
Fair Value	39,404	39,472
Private label mortgage backed security
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	5,501	5,684
Gross Unrealized Gains	187	3
Fair Value	5,688	5,687
Mortgage backed securities - residential
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	171,021	190,569
Gross Unrealized Gains	6,186	6,641
Fair Value	177,207	197,210
Collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	197,547	194,427
Gross Unrealized Gains	2,003	1,580
Gross Unrealized Losses	(406)	(130)
Fair Value	$ 199,144	$ 195,877

Gross Amortized Cost and Fair Value of Securities Available for Sale and Related Gross Unrealized Gains and Losses Recognized in Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)
In Thousands, unless otherwise specified

Mar. 31, 2013

Dec. 31, 2012

Schedule of Available-for-sale Securities [Line Items]

Gross Amortized Cost

$ 413,023

$ 429,611

Gross Unrealized Gains

8,830

8,771

Gross Unrealized Losses

(410)

(136)

Fair Value

421,443

438,246

U.S. Treasury securities and U.S. Government agencies

Schedule of Available-for-sale Securities [Line Items]

Gross Amortized Cost

38,954

38,931

Gross Unrealized Gains

454

547

Gross Unrealized Losses

(4)

(6)

Fair Value

39,404

39,472

Private label mortgage backed security

Schedule of Available-for-sale Securities [Line Items]

Gross Amortized Cost

5,501

5,684

Gross Unrealized Gains

187

Fair Value

5,688

5,687

Mortgage backed securities - residential

Schedule of Available-for-sale Securities [Line Items]

Gross Amortized Cost

171,021

190,569

Gross Unrealized Gains

6,186

6,641

Fair Value

177,207

197,210

Collateralized mortgage obligations

Schedule of Available-for-sale Securities [Line Items]

Gross Amortized Cost

197,547

194,427

Gross Unrealized Gains

2,003

1,580

Gross Unrealized Losses

(406)

(130)

Fair Value

$ 199,144

$ 195,877

- Definition

This item represents the cost of debt and equity 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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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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