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	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	$ 429,611	$ 639,579
Gross Unrealized Gains	8,771	8,438
Gross Unrealized Losses	(136)	(2,069)
Fair Value	438,246	645,948
U.S. Treasury securities and U.S. Government agencies
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	38,931	152,085
Gross Unrealized Gains	547	814
Gross Unrealized Losses	(6)	(225)
Fair Value	39,472	152,674
Private label mortgage backed and other private label mortgage-related securities
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	5,684	5,818
Gross Unrealized Gains	3
Gross Unrealized Losses		(1,276)
Fair Value	5,687	4,542
Mortgage backed securities - residential
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	190,569	287,013
Gross Unrealized Gains	6,641	6,343
Gross Unrealized Losses		(27)
Fair Value	197,210	293,329
Collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Cost	194,427	194,663
Gross Unrealized Gains	1,580	1,281
Gross Unrealized Losses	(130)	(541)
Fair Value	$ 195,877	$ 195,403

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

Dec. 31, 2012

Dec. 31, 2011

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

Gross Amortized Cost

$ 429,611

$ 639,579

Gross Unrealized Gains

8,771

8,438

Gross Unrealized Losses

(136)

(2,069)

Fair Value

438,246

645,948

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

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

Gross Amortized Cost

38,931

152,085

Gross Unrealized Gains

547

814

Gross Unrealized Losses

(6)

(225)

Fair Value

39,472

152,674

Private label mortgage backed and other private label mortgage-related securities

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

Gross Amortized Cost

5,684

5,818

Gross Unrealized Gains

Gross Unrealized Losses

(1,276)

Fair Value

5,687

4,542

Mortgage backed securities - residential

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

Gross Amortized Cost

190,569

287,013

Gross Unrealized Gains

6,641

6,343

Gross Unrealized Losses

(27)

Fair Value

197,210

293,329

Collateralized mortgage obligations

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

Gross Amortized Cost

194,427

194,663

Gross Unrealized Gains

1,580

1,281

Gross Unrealized Losses

(130)

(541)

Fair Value

$ 195,877

$ 195,403

- 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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