Investment Securities (Schedule Of Amortized Cost And Fair Values Of Investment Securities, With Gross Unrealized Gains And Losses) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities held to maturity, Amortized Cost	$ 205,062	$ 192,764
Securities held to maturity, Gross Unrealized Gains	6,702	6,403
Securities held to maturity, Gross Unrealized Losses	(266)	(57)
Securities held to maturity, Estimated Fair Value	211,498	199,110
Securities available for sale, Amortized Cost	1,706,916	1,765,597
Securities available for sale, Gross Unrealized Gains	40,134	40,528
Securities available for sale, Gross Unrealized Losses	(2,046)	(920)
Securities available for sale, Estimated Fair Value	1,745,004	1,805,205
U.S. Government-Sponsored Enterprises Obligations [Member]
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities held to maturity, Amortized Cost	69,949	85,172
Securities held to maturity, Gross Unrealized Gains	1,244	1,921
Securities held to maturity, Gross Unrealized Losses
Securities held to maturity, Estimated Fair Value	71,193	87,093
Securities available for sale, Amortized Cost	281,746	336,859
Securities available for sale, Gross Unrealized Gains	4,364	5,633
Securities available for sale, Gross Unrealized Losses	(386)	(4)
Securities available for sale, Estimated Fair Value	285,724	342,488
Obligations Of State And Political Subdivisions [Member]
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities held to maturity, Amortized Cost	88,909	81,053
Securities held to maturity, Gross Unrealized Gains	4,730	3,682
Securities held to maturity, Gross Unrealized Losses	(113)	(57)
Securities held to maturity, Estimated Fair Value	93,526	84,678
Securities available for sale, Amortized Cost	120,680	137,503
Securities available for sale, Gross Unrealized Gains	6,573	6,500
Securities available for sale, Gross Unrealized Losses	(178)	(198)
Securities available for sale, Estimated Fair Value	127,075	143,805
Mortgage Backed Securities[Member]
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities held to maturity, Amortized Cost	46,204	26,539
Securities held to maturity, Gross Unrealized Gains	728	800
Securities held to maturity, Gross Unrealized Losses	(153)
Securities held to maturity, Estimated Fair Value	46,779	27,339
Securities available for sale, Amortized Cost	1,303,030	1,289,775
Securities available for sale, Gross Unrealized Gains	29,108	28,317
Securities available for sale, Gross Unrealized Losses	(1,482)	(718)
Securities available for sale, Estimated Fair Value	1,330,656	1,317,374
Other Securities [Member]
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities available for sale, Amortized Cost	1,460	1,460
Securities available for sale, Gross Unrealized Gains	89	78
Securities available for sale, Gross Unrealized Losses
Securities available for sale, Estimated Fair Value	$ 1,549	$ 1,538

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

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+ Details

- 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.

+ References+ Details

- 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.

+ References+ Details

- Definition

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity.

+ References

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-Paragraph 1

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

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+ Details

- Definition

This item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.

+ References+ Details

- Definition

As of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.

+ References+ Details

- Definition

As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.

+ References+ Details