Investment Securities (Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	$ 3,059,638	$ 2,736,054
Available-for-sale securities, unrealized gains	12,298	9,201
Available-for-sale securities, unrealized losses	(24,578)	(44,035)
Available for sale, at fair value	3,047,358	2,701,220
Held to maturity, at amortized cost	3,905	4,216
Held-to-maturity securities, unrealized gains	1,114	1,001
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	5,019	5,217
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	40,026
Available-for-sale securities, unrealized gains	0
Available-for-sale securities, unrealized losses	0
Available for sale, at fair value	40,026
Obligations Of States And Political Subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	291,908	305,708
Available-for-sale securities, unrealized gains	6,775	5,526
Available-for-sale securities, unrealized losses	(889)	(3,537)
Available for sale, at fair value	297,794	307,697
Residential Mortgage-Backed Securities And Collateralized Mortgage Obligations
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	2,725,745	2,428,387
Available-for-sale securities, unrealized gains	5,499	3,664
Available-for-sale securities, unrealized losses	(23,689)	(40,498)
Available for sale, at fair value	2,707,555	2,391,553
Held to maturity, at amortized cost	3,905	4,216
Held-to-maturity securities, unrealized gains	1,114	1,001
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	5,019	5,217
Investments In Mutual Funds And Other Equity Securities
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	1,959	1,959
Available-for-sale securities, unrealized gains	24	11
Available-for-sale securities, unrealized losses	0	0
Available for sale, at fair value	$ 1,983	$ 1,970

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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