Investments (Schedule Of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,164,848	$ 1,623,319
Gross Unrealized Gains	544	823
Gross Unrealized Losses	(7,458)	(7,298)
Fair Value	1,157,934	1,616,844
Agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	314,982	441,315
Gross Unrealized Gains	333	509
Gross Unrealized Losses	(2,367)	(2,760)
Fair Value	312,948	439,064
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	612,698	810,444
Gross Unrealized Gains	116	268
Gross Unrealized Losses	(4,156)	(3,020)
Fair Value	608,658	807,692
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,500	3,965
Gross Unrealized Gains	4	2
Gross Unrealized Losses	0	(2)
Fair Value	2,504	3,965
Government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	234,668	367,595
Gross Unrealized Gains	91	44
Gross Unrealized Losses	(935)	(1,516)
Fair Value	$ 233,824	$ 366,123

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Section 50
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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