Fixed Maturity Securities In An Unrealized Loss Position (Non-Investment Grade Fixed Maturity Securities) (Details) $ in Thousands	Mar. 31, 2023 USD ($) position	Dec. 31, 2022 USD ($)
Corporate
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	$ 5,869,295	$ 6,040,137
Gross Unrealized Loss	340,440	406,746
State and municipal
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	2,079,792	2,319,240
Gross Unrealized Loss	127,420	168,592
Mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	1,632,585	1,572,867
Gross Unrealized Loss	166,440	190,958
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	3,406,951	3,746,285
Gross Unrealized Loss	$ 117,853	$ 152,322
Noninvestment Grade Investments at Loss Position
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	65
Aggregate Fair Value	$ 167,130
Gross Unrealized Loss	$ 71,448
Noninvestment Grade Investments at Loss Position \| Foreign government
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	33
Aggregate Fair Value	$ 105,347
Gross Unrealized Loss	$ 64,516
Noninvestment Grade Investments at Loss Position \| Corporate
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	16
Aggregate Fair Value	$ 45,507
Gross Unrealized Loss	$ 3,789
Noninvestment Grade Investments at Loss Position \| State and municipal
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	1
Aggregate Fair Value	$ 12,066
Gross Unrealized Loss	$ 2,936
Noninvestment Grade Investments at Loss Position \| Mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	14
Aggregate Fair Value	$ 4,202
Gross Unrealized Loss	$ 199
Noninvestment Grade Investments at Loss Position \| Asset-backed
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	1
Aggregate Fair Value	$ 8
Gross Unrealized Loss	$ 8

Amount of 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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922888-210455

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456

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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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Number of investments in debt securities 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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