Fair Value of Assets and Liabilities (Quantitative Info for Level 3 Inputs) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022		Sep. 30, 2022
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Corporate securities	$ 232,311	$ 148,179
Market risk benefits assets	2,519,234	1,393,237	[1]	$ 1,306,000
Market risk benefit liabilities	4,371,178	5,521,601	[1]	$ 5,945,000
Fair Value, Measurements, Recurring
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Market risk benefits assets	2,519,234	1,393,237
Market risk benefit liabilities	4,371,178	5,521,601
Policyholders’ account balances	6,005,729	3,502,096
Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Funds held under reinsurance agreements	$ 10,000,000
Level 3 | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Policyholder Age	50 years
Level 3 | Minimum | Market risk benefit liabilities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Mortality rate	0.00%
Level 3 | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Policyholder Age	90 years
Level 3 | Fair Value, Measurements, Recurring
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Market risk benefits assets	$ 2,519,234	1,393,237
Market risk benefit liabilities	4,371,178	5,521,601
Policyholders’ account balances	$ 6,005,729	$ 3,502,096
Level 3 | Internal | Minimum | Discounted cash flow | Market risk benefit liabilities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Lapse rate	1.00%	1.00%
Spread over SOFR	0.48%	0.50%
Utilization rate	38.00%	38.00%
Withdrawal rate (greater than maximum range)	81.00%	77.00%
Mortality rate	0.00%	0.00%
Equity volatility curve	15.00%	18.00%
Level 3 | Internal | Minimum | Discounted cash flow | Policyholders' account balances
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Lapse rate	1.00%	1.00%
Spread over SOFR	0.48%	0.22%
Mortality rate	0.00%	0.00%
Equity volatility curve	6.00%	6.00%
Option budget	(1.00%)	(2.00%)
Level 3 | Internal | Minimum | Discounted cash flow | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Discount rate	8.23%	9.77%
Level 3 | Internal | Minimum | Discounted cash flow | Market risk benefit assets
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Lapse rate	1.00%	1.00%
Spread over SOFR	0.48%	0.50%
Utilization rate	38.00%	38.00%
Withdrawal rate (greater than maximum range)	81.00%	77.00%
Mortality rate	0.00%	0.00%
Equity volatility curve	15.00%	18.00%
Level 3 | Internal | Minimum | Market comparables | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
EBITDA multiples		2.2
Level 3 | Internal | Minimum | Liquidation | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Liquidation value	63.62%
Level 3 | Internal | Maximum | Discounted cash flow | Market risk benefit liabilities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Lapse rate	20.00%	20.00%
Spread over SOFR	2.10%	2.20%
Utilization rate	95.00%	95.00%
Withdrawal rate (greater than maximum range)	100.00%	100.00%
Mortality rate	15.00%	15.00%
Equity volatility curve	25.00%	26.00%
Level 3 | Internal | Maximum | Discounted cash flow | Policyholders' account balances
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Lapse rate	80.00%	80.00%
Spread over SOFR	2.15%	2.26%
Mortality rate	23.00%	23.00%
Equity volatility curve	28.00%	30.00%
Option budget	6.00%	6.00%
Level 3 | Internal | Maximum | Discounted cash flow | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Discount rate	20.00%	20.00%
Level 3 | Internal | Maximum | Discounted cash flow | Market risk benefit assets
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Lapse rate	20.00%	20.00%
Spread over SOFR	2.10%	2.20%
Utilization rate	95.00%	95.00%
Withdrawal rate (greater than maximum range)	100.00%	100.00%
Mortality rate	15.00%	15.00%
Equity volatility curve	25.00%	26.00%
Level 3 | Internal | Maximum | Market comparables | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
EBITDA multiples		23.5
Level 3 | Internal | Maximum | Liquidation | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Liquidation value	63.62%
Level 3 | Internal | Weighted Average | Discounted cash flow | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Discount rate	12.16%	16.53%
Level 3 | Internal | Weighted Average | Market comparables | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
EBITDA multiples		8.1
Level 3 | Internal | Weighted Average | Liquidation | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Liquidation value	63.62%
Level 3 | Internal | Fair Value, Measurements, Recurring | Market risk benefit liabilities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Market risk benefit liabilities	$ 4,371,178	$ 5,521,601
Level 3 | Internal | Fair Value, Measurements, Recurring | Policyholders' account balances
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Policyholders’ account balances	6,005,729	3,502,096
Level 3 | Internal | Fair Value, Measurements, Recurring | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Corporate securities	726,528	408,494
Level 3 | Internal | Fair Value, Measurements, Recurring | Market risk benefit assets
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Market risk benefits assets	$ 2,519,234	$ 1,393,237

[1] Prior period amounts adjusted for the implementation of Accounting Standard Update ("ASU") 2018-12: Targeted Improvements to the Accounting for Long-Duration Contracts.