Investment Securities (Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	$ 3,022,138	$ 3,099,329
Available-for-sale securities, unrealized gains	4,251	8,256
Available-for-sale securities, unrealized losses	(78,975)	(41,816)
Available for sale, at fair value	2,947,414	3,065,769
Held to maturity, at amortized cost	3,667	3,803
Held-to-maturity securities, unrealized gains	1,002	1,103
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	4,669	4,906
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	40,017	40,021
Available-for-sale securities, unrealized gains	0	0
Available-for-sale securities, unrealized losses	(499)	(323)
Available for sale, at fair value	39,518	39,698
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	299,855	303,352
Available-for-sale securities, unrealized gains	3,295	6,206
Available-for-sale securities, unrealized losses	(3,599)	(1,102)
Available for sale, at fair value	299,551	308,456
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	2,682,266	2,703,997
Available-for-sale securities, unrealized gains	956	2,039
Available-for-sale securities, unrealized losses	(74,877)	(40,391)
Available for sale, at fair value	2,608,345	2,665,645
Held to maturity, at amortized cost	3,667	3,803
Held-to-maturity securities, unrealized gains	1,002	1,103
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	$ 4,669	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
-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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Fair value of investments in debt securities classified as held-to-maturity.

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