Investment Securities (Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	$ 2,934,189	$ 3,099,329
Available-for-sale securities, unrealized gains	3,495	8,256
Available-for-sale securities, unrealized losses	(83,286)	(41,816)
Available for sale, at fair value	2,854,398	3,065,769
Investment securities held to maturity	3,586	3,803
Held-to-maturity securities, unrealized gains	1,038	1,103
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	4,624	4,906
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	40,012	40,021
Available-for-sale securities, unrealized gains	0	0
Available-for-sale securities, unrealized losses	(548)	(323)
Available for sale, at fair value	39,464	39,698
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	293,391	303,352
Available-for-sale securities, unrealized gains	2,838	6,206
Available-for-sale securities, unrealized losses	(3,715)	(1,102)
Available for sale, at fair value	292,514	308,456
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	2,600,786	2,703,997
Available-for-sale securities, unrealized gains	657	2,039
Available-for-sale securities, unrealized losses	(79,023)	(40,391)
Available for sale, at fair value	2,522,420	2,665,645
Investment securities held to maturity	3,586	3,803
Held-to-maturity securities, unrealized gains	1,038	1,103
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	$ 4,624	4,906
Investments in mutual funds and other securities
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost		51,959
Available-for-sale securities, unrealized gains		11
Available-for-sale securities, unrealized losses		0
Available for sale, at fair value		$ 51,970

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
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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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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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