Fixed Maturity Securities In An Unrealized Loss Position (Non-Investment Grade Fixed Maturity Securities) (Details) $ in Thousands	Jun. 30, 2023 USD ($) position	Dec. 31, 2022 USD ($)
Noninvestment Grade Investments at Loss Position
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	59
Aggregate Fair Value	$ 143,076
Gross Unrealized Loss	$ 82,888
Foreign government \| Noninvestment Grade Investments at Loss Position
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	28
Aggregate Fair Value	$ 104,753
Gross Unrealized Loss	76,573
Corporate
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	6,363,534	$ 6,040,137
Gross Unrealized Loss	$ 378,384	406,746
Corporate \| Noninvestment Grade Investments at Loss Position
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	14
Aggregate Fair Value	$ 25,942
Gross Unrealized Loss	4,052
State and municipal
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	2,210,995	2,319,240
Gross Unrealized Loss	$ 144,995	168,592
State and municipal \| Noninvestment Grade Investments at Loss Position
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	1
Aggregate Fair Value	$ 7,971
Gross Unrealized Loss	2,031
Mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	1,752,868	1,572,867
Gross Unrealized Loss	$ 190,029	190,958
Mortgage-backed \| Noninvestment Grade Investments at Loss Position
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	14
Aggregate Fair Value	$ 4,393
Gross Unrealized Loss	226
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	3,406,690	3,746,285
Gross Unrealized Loss	$ 116,036	$ 152,322
Asset-backed \| Noninvestment Grade Investments at Loss Position
Debt Securities, Available-for-sale [Line Items]
Number of Securities \| position	2
Aggregate Fair Value	$ 17
Gross Unrealized Loss	$ 6

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.

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