Fair Value of Assets and Liabilities (Quantitative Info for Level 3 Inputs) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Corporate securities	$ 283,560	$ 279,096
Policyholders’ account balances	10,958,077	9,181,459
Fair Value, Measurements, Recurring
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Future policy benefits	10,511,815	17,314,004
Policyholders’ account balances	$ 986,479	580,184
Level 3 | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Policyholder Age	45 years
Level 3 | Minimum     | Future policy benefits
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]
Future policy benefits	$ 10,511,815	17,314,004
Policyholders’ account balances	$ 986,479	$ 580,184
Level 3 | Internal | Minimum     | Discounted cash flow | Future policy benefits
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Lapse rate	1.00%	1.00%
Spread over LIBOR	0.09%	0.06%
Utilization rate	39.00%	39.00%
Withdrawal rate (greater than maximum range)	76.00%	76.00%
Mortality rate	0.00%	0.00%
Equity volatility curve	17.00%	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 LIBOR	0.09%	0.06%
Equity volatility curve	6.00%	6.00%
Level 3 | Internal | Minimum     | Discounted cash flow | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Discount rate	1.37%	0.99%
Level 3 | Internal | Minimum     | Valuation, Cost Approach | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Liquidation value	71.23%
Level 3 | Internal | Maximum     | Discounted cash flow | Future policy benefits
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Lapse rate	20.00%	20.00%
Spread over LIBOR	1.14%	1.17%
Utilization rate	96.00%	96.00%
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	42.00%	40.00%
Spread over LIBOR	1.14%	1.17%
Equity volatility curve	42.00%	42.00%
Level 3 | Internal | Maximum     | Discounted cash flow | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Discount rate	20.25%	20.00%
Level 3 | Internal | Maximum     | Valuation, Cost Approach | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Liquidation value	71.23%
Level 3 | Internal | Weighted Average | Discounted cash flow | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Discount rate	6.60%	6.53%
Level 3 | Internal | Weighted Average | Valuation, Cost Approach | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Liquidation value	71.23%
Level 3 | Internal | Fair Value, Measurements, Recurring | Future policy benefits
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Future policy benefits	$ 10,511,815	$ 17,314,004
Level 3 | Internal | Fair Value, Measurements, Recurring | Policyholders' account balances
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Policyholders’ account balances	986,479	580,184
Level 3 | Internal | Fair Value, Measurements, Recurring | Corporate securities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Corporate securities	99,645	59,960
Level 3 | Internal | Fair Value, Measurements, Recurring | Reinsurance recoverables
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Reinsurance recoverables	$ 271,390	$ 409,013