Investment Securities (Summary Of Available For Sale Investment Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 3,543,119	$ 3,595,798
Gross Unrealized Gains	41,855	19,303
Gross Unrealized Losses	(2,730)	(27,283)
Fair Value	3,582,244	3,587,818
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	43,147	43,125
Gross Unrealized Gains	559	232
Gross Unrealized Losses	0	0
Fair Value	43,706	43,357
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,016	13,087
Gross Unrealized Gains	534	536
Gross Unrealized Losses	0	0
Fair Value	13,550	13,623
Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	126,305	126,520
Gross Unrealized Gains	297	389
Gross Unrealized Losses	0	0
Fair Value	126,602	126,909
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	191,386	209,785
Gross Unrealized Gains	2,653	1,340
Gross Unrealized Losses	(143)	(1,121)
Fair Value	193,896	210,004
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,599,118	2,645,107
Gross Unrealized Gains	24,787	7,874
Gross Unrealized Losses	(1,771)	(22,562)
Fair Value	2,622,134	2,630,419
Collateralized Mortgage Obligations Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	542,761	530,426
Gross Unrealized Gains	7,687	2,396
Gross Unrealized Losses	(393)	(3,225)
Fair Value	550,055	529,597
State And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,964	4,343
Gross Unrealized Gains	76	92
Gross Unrealized Losses	(1)	(1)
Fair Value	4,039	4,434
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,228	3,228
Gross Unrealized Gains	4,976	6,444
Gross Unrealized Losses	0	0
Fair Value	8,204	9,672
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,194	20,177
Gross Unrealized Gains	286	0
Gross Unrealized Losses	(422)	(374)
Fair Value	$ 20,058	$ 19,803

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
-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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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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