Investment Securities (Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	$ 2,973,447	$ 3,099,329
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,860	8,256
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	111,913	41,816
Available for sale, at fair value	2,864,394	3,065,769
Investment securities held to maturity	3,672	3,803
Held-to-maturity securities, unrealized gains	1,056	1,103
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	4,728	4,906
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	40,007	40,021
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	538	323
Available for sale, at fair value	39,469	39,698
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	297,720	303,352
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,894	6,206
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4,950	1,102
Available for sale, at fair value	294,664	308,456
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	2,635,720	2,703,997
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	966	2,039
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	106,425	40,391
Available for sale, at fair value	2,530,261	2,665,645
Investment securities held to maturity	3,672	3,803
Held-to-maturity securities, unrealized gains	1,056	1,103
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	$ 4,728	4,906
Investments in mutual funds and other securities
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost		51,959
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		11
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		0
Available for sale, at fair value		$ 51,970

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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Amount of accumulated unrealized loss 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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