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Fixed Maturity Securities In An Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	$ 4,195,463	$ 2,552,830
Gross Unrealized Losses, Less than 12 Months	47,863	42,788
Fair Value, 12 Months or Greater	837,540	747,568
Gross Unrealized Losses, 12 Months or Greater	51,231	51,404
Fair Value, Total	5,033,003	3,300,398
Gross Unrealized Losses, Total	99,094	94,192
U.S. government and government agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	57,625	47,649
Gross Unrealized Losses, Less than 12 Months	913	347
Fair Value, 12 Months or Greater	462	17
Gross Unrealized Losses, 12 Months or Greater	2	0
Fair Value, Total	58,087	47,666
Gross Unrealized Losses, Total	915	347
State and municipal
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	288,083	147,754
Gross Unrealized Losses, Less than 12 Months	4,949	1,165
Fair Value, 12 Months or Greater	20,219	20,528
Gross Unrealized Losses, 12 Months or Greater	1,232	904
Fair Value, Total	308,302	168,282
Gross Unrealized Losses, Total	6,181	2,069
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	322,410	212,388
Gross Unrealized Losses, Less than 12 Months	11,927	5,121
Fair Value, 12 Months or Greater	30,537	23,943
Gross Unrealized Losses, 12 Months or Greater	374	230
Fair Value, Total	352,947	236,331
Gross Unrealized Losses, Total	12,301	5,351
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	1,803,588	1,389,133
Gross Unrealized Losses, Less than 12 Months	4,917	6,563
Fair Value, 12 Months or Greater	652,450	656,877
Gross Unrealized Losses, 12 Months or Greater	13,243	26,934
Fair Value, Total	2,456,038	2,046,010
Gross Unrealized Losses, Total	18,160	33,497
Corporate
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	1,414,453	612,177
Gross Unrealized Losses, Less than 12 Months	15,904	6,721
Fair Value, 12 Months or Greater	113,498	39,985
Gross Unrealized Losses, 12 Months or Greater	3,214	1,759
Fair Value, Total	1,527,951	652,162
Gross Unrealized Losses, Total	19,118	8,480
Foreign government
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	309,304	143,729
Gross Unrealized Losses, Less than 12 Months	9,253	22,871
Fair Value, 12 Months or Greater	20,374	6,218
Gross Unrealized Losses, 12 Months or Greater	33,166	21,577
Fair Value, Total	329,678	149,947
Gross Unrealized Losses, Total	$ 42,419	$ 44,448

X

- Definition

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.

+ References

No definition available.

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X

- Definition

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

+ References

No definition available.

+ Details

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- Definition

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Debt Securities, Available-for-sale and Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss

+ References

No definition available.

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- Definition

Debt Securities, Available-for-sale and Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss

+ References

No definition available.

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- Definition

Debt Securities, Available-for-sale and Held-to-maturity, Unrealized Loss Position, Accumulated Loss

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No definition available.

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