Investment Securities (Schedule Of Amortized Cost And Fair Values Of Investment Securities, With Gross Unrealized Gains And Losses) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities available for sale, Amortized Cost	$ 1,775,213	$ 1,765,597
Securities available for sale, Gross Unrealized Gains	37,147	40,528
Securities available for sale, Gross Unrealized Losses	(1,337)	(920)
Securities available for sale, Fair Value	1,811,023	1,805,205
Securities held to maturity, Amortized Cost	190,084	192,764
Securities held to maturity, Gross Unrealized Gains	6,172	6,403
Securities held to maturity, Gross Unrealized Losses	(73)	(57)
Securities held to maturity, Fair Value	196,183	199,110
U.S. Government-Sponsored Enterprise Obligations [Member]
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities available for sale, Amortized Cost	306,811	336,859
Securities available for sale, Gross Unrealized Gains	3,075	5,633
Securities available for sale, Gross Unrealized Losses	(167)	(4)
Securities available for sale, Fair Value	309,719	342,488
Securities held to maturity, Amortized Cost	85,095	85,172
Securities held to maturity, Gross Unrealized Gains	1,683	1,921
Securities held to maturity, Fair Value	86,778	87,093
Obligations Of State And Political Subdivisions [Member]
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities available for sale, Amortized Cost	131,870	137,503
Securities available for sale, Gross Unrealized Gains	6,350	6,500
Securities available for sale, Gross Unrealized Losses	(191)	(198)
Securities available for sale, Fair Value	138,029	143,805
Securities held to maturity, Amortized Cost	80,486	81,053
Securities held to maturity, Gross Unrealized Gains	3,730	3,682
Securities held to maturity, Gross Unrealized Losses	(73)	(57)
Securities held to maturity, Fair Value	84,143	84,678
Mortgage Backed Securities [Member]
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities available for sale, Amortized Cost	1,335,071	1,289,775
Securities available for sale, Gross Unrealized Gains	27,647	28,317
Securities available for sale, Gross Unrealized Losses	(979)	(718)
Securities available for sale, Fair Value	1,361,739	1,317,374
Securities held to maturity, Amortized Cost	24,503	26,539
Securities held to maturity, Gross Unrealized Gains	759	800
Securities held to maturity, Gross Unrealized Losses
Securities held to maturity, Fair Value	25,262	27,339
Other Securities [Member]
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Securities available for sale, Amortized Cost	1,461	1,460
Securities available for sale, Gross Unrealized Gains	75	78
Securities available for sale, Gross Unrealized Losses
Securities available for sale, Fair Value	$ 1,536	$ 1,538

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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-Name Accounting Standards Codification

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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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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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

-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