Investment Securities Available for Sale (Summary Of Available For Sale Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 4,038,239	$ 3,768,618
Gross Unrealized Gains	6,107	11,114
Gross Unrealized Losses	(57,277)	(61,537)
Fair Value	3,987,069	3,718,195
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	83,608	108,221
Gross Unrealized Gains	0	225
Gross Unrealized Losses	(934)	(644)
Fair Value	82,674	107,802
U.S. Government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,771	12,727
Gross Unrealized Gains	91	266
Gross Unrealized Losses	0	0
Fair Value	10,862	12,993
Mortgage-backed securities issued by U.S. Government agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	121,283	174,440
Gross Unrealized Gains	519	1,116
Gross Unrealized Losses	(1,362)	(1,354)
Fair Value	120,440	174,202
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,666,818	2,543,495
Gross Unrealized Gains	5,059	5,416
Gross Unrealized Losses	(31,354)	(42,571)
Fair Value	2,640,523	2,506,340
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,135,259	905,789
Gross Unrealized Gains	144	1,214
Gross Unrealized Losses	(23,404)	(16,561)
Fair Value	1,111,999	890,442
State and municipal securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	180	2,780
Gross Unrealized Gains	0	14
Gross Unrealized Losses	0	0
Fair Value	180	2,794
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		919
Gross Unrealized Gains		2,863
Gross Unrealized Losses		0
Fair Value		3,782
Corporate debt and other securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,320	20,247
Gross Unrealized Gains	294	0
Gross Unrealized Losses	(223)	(407)
Fair Value	$ 20,391	$ 19,840

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 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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