Investment Securities (Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	$ 2,803,288	$ 3,045,887
Available-for-sale securities, unrealized gains	44,015	6,375
Available-for-sale securities, unrealized losses	(5,227)	(75,154)
Available for sale, at fair value	2,842,076	2,977,108
Investment securities held to maturity	3,320	3,606
Held-to-maturity securities, unrealized gains	1,018	1,038
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	4,338	4,644
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	576,089	40,002
Available-for-sale securities, unrealized gains	11,379	0
Available-for-sale securities, unrealized losses	(268)	(346)
Available for sale, at fair value	587,200	39,656
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	258,853	308,972
Available-for-sale securities, unrealized gains	10,212	2,785
Available-for-sale securities, unrealized losses	(35)	(2,586)
Available for sale, at fair value	269,030	309,171
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	1,968,346	2,696,913
Available-for-sale securities, unrealized gains	22,424	3,590
Available-for-sale securities, unrealized losses	(4,924)	(72,222)
Available for sale, at fair value	1,985,846	2,628,281
Investment securities held to maturity	3,320	3,606
Held-to-maturity securities, unrealized gains	1,018	1,038
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	$ 4,338	$ 4,644

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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