Investment Securities (Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	$ 3,099,329	$ 2,736,054
Available-for-sale securities, unrealized gains	8,256	9,201
Available-for-sale securities, unrealized losses	(41,816)	(44,035)
Available for sale, at fair value	3,065,769	2,701,220
Held to maturity, at amortized cost	3,803	4,216
Held-to-maturity securities, unrecognized gains	1,103	1,001
Held-to-maturity securities, unrecognized losses	0	0
Held-to-maturity securities, fair value	4,906	5,217
US Treasury and Government [Member]
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	40,021
Available-for-sale securities, unrealized gains	0
Available-for-sale securities, unrealized losses	(323)
Available for sale, at fair value	39,698
Obligations Of States And Political Subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	303,352	305,708
Available-for-sale securities, unrealized gains	6,206	5,526
Available-for-sale securities, unrealized losses	(1,102)	(3,537)
Available for sale, at fair value	308,456	307,697
Residential Mortgage-Backed Securities And Collateralized Mortgage Obligations
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	2,703,997	2,428,387
Available-for-sale securities, unrealized gains	2,039	3,664
Available-for-sale securities, unrealized losses	(40,391)	(40,498)
Available for sale, at fair value	2,665,645	2,391,553
Held to maturity, at amortized cost	3,803	4,216
Held-to-maturity securities, unrecognized gains	1,103	1,001
Held-to-maturity securities, unrecognized losses	0	0
Held-to-maturity securities, fair value	4,906	5,217
Investments In Mutual Funds And Other Equity Securities
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	51,959	1,959
Available-for-sale securities, unrealized gains	11	11
Available-for-sale securities, unrealized losses	0	0
Available for sale, at fair value	$ 51,970	$ 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
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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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