Investment Securities Available for Sale (Summary Of Available For Sale Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 3,768,618	$ 3,595,798
Gross Unrealized Gains	11,114	19,303
Gross Unrealized Losses	(61,537)	(27,283)
Fair Value	3,718,195	3,587,818
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	108,221	43,125
Gross Unrealized Gains	225	232
Gross Unrealized Losses	(644)	0
Fair Value	107,802	43,357
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,727	13,087
Gross Unrealized Gains	266	536
Gross Unrealized Losses	0	0
Fair Value	12,993	13,623
Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		126,520
Gross Unrealized Gains		389
Gross Unrealized Losses		0
Fair Value		126,909
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	174,440	209,785
Gross Unrealized Gains	1,116	1,340
Gross Unrealized Losses	(1,354)	(1,121)
Fair Value	174,202	210,004
Mortgage-Backed Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,543,495	2,645,107
Gross Unrealized Gains	5,416	7,874
Gross Unrealized Losses	(42,571)	(22,562)
Fair Value	2,506,340	2,630,419
Collateralized Mortgage Obligations Issued by U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	905,789	530,426
Gross Unrealized Gains	1,214	2,396
Gross Unrealized Losses	(16,561)	(3,225)
Fair Value	890,442	529,597
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,780	4,343
Gross Unrealized Gains	14	92
Gross Unrealized Losses	0	(1)
Fair Value	2,794	4,434
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	919	3,228
Gross Unrealized Gains	2,863	6,444
Gross Unrealized Losses	0	0
Fair Value	3,782	9,672
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,247	20,177
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(407)	(374)
Fair Value	$ 19,840	$ 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
-Subparagraph (b)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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