Available-For-Sale And Held-To-Maturity Securities (Schedule Of Gross Unrealized Losses And The Estimated Fair Value By Length Of Time In A Loss Position) (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	$ (85,317)
Available-for-sale Securities, Estimated fair value, Less than 12 months	1,674,503
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(40,524)
Available-for-sale Securities, Estimated fair value, 12 months or more	477,451
Available-for-sale Securities, Gross unrealized losses, Total	(125,841)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	2,151,954
Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(122)
Available-for-sale Securities, Estimated fair value, Less than 12 months	23,806
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(33)
Available-for-sale Securities, Estimated fair value, 12 months or more	10,315
Available-for-sale Securities, Gross unrealized losses, Total	(155)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	34,121
Commercial [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(482)
Available-for-sale Securities, Estimated fair value, Less than 12 months	61,706
Available-for-sale Securities, Gross unrealized losses, Total	(482)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	61,706
Non-Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(94)
Available-for-sale Securities, Estimated fair value, 12 months or more	817
Available-for-sale Securities, Gross unrealized losses, Total	(94)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	817
Corporate Fixed Income Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(17,089)
Available-for-sale Securities, Estimated fair value, Less than 12 months	492,713
Available-for-sale Securities, Gross unrealized losses, Total	(17,089)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	492,713
Asset-Backed Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(67,624)
Available-for-sale Securities, Estimated fair value, Less than 12 months	1,096,278
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(40,397)
Available-for-sale Securities, Estimated fair value, 12 months or more	466,319
Available-for-sale Securities, Gross unrealized losses, Total	(108,021)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 1,562,597

Schedule of available for sale and held to maturity securities.

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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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