Fair Value of Financial Instruments - Carrying Values and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands		Dec. 19, 2022	Jun. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale debt securities, at fair value			$ 2,357,154	$ 2,356,996
Fixed-maturity security held to maturity, fair value			1,495,594	1,299,102
Equity securities			33,689	40,684
Separate account assets			2,377,654	2,485,745
Surplus note			1,277,970	1,183,728
Separate account liabilities			2,377,654	2,485,745
Fixed-maturity security (held-to-maturity)			1,278,580	1,184,370
Reported Value Measurement [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale debt securities, at fair value			2,357,154	2,356,996
Equity securities			33,689	40,684
Trading securities			22,399	43,233
Separate account assets			2,377,654	2,485,745
Separate account liabilities			2,377,654	2,485,745
Reported Value Measurement [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Policy loans	[1]		31,471	32,927
Surplus note	[1],[2]		1,277,970	1,183,728
Fixed-maturity security (held-to-maturity)	[1]	$ 1,278,580		1,184,370
Reported Value Measurement [Member] | Level 3 [Member] | Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Deposit asset underlying 10% coinsurance agreement	[1]		235,066	233,499
Reported Value Measurement [Member] | Senior Notes [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Notes payable	[2],[3]		374,226	374,037
Estimate of Fair Value Measurement [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale debt securities, at fair value			2,357,154	2,356,996
Equity securities			33,689	40,684
Trading securities			22,399	43,233
Separate account assets			2,377,654	2,485,745
Separate account liabilities			2,377,654	2,485,745
Estimate of Fair Value Measurement [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed-maturity security held to maturity, fair value	[1]		1,495,594	1,299,102
Policy loans	[1]		31,471	32,927
Surplus note	[1],[2]		1,482,037	1,296,972
Estimate of Fair Value Measurement [Member] | Level 3 [Member] | Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Deposit asset underlying 10% coinsurance agreement	[1]		235,066	233,499
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Notes payable	[2],[3]		$ 395,110	$ 395,522

[1] Classified as a Level 3 fair value measurement.

[2] Carrying value amounts shown are net of issuance costs

[3] Classified as a Level 2 fair value measurement.