Certain Long-Duration Contracts with Guarantees (Variable Annuity, Variable Life, Variable Universal Life and Universal Life Contracts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Annuity Contracts | Return of net deposits | In the Event of Death
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	$ 104,700,706	$ 101,413,706
Net amount at risk	$ 18,336	$ 23,061
Average attained age of contractholders	68 years	67 years
Annuity Contracts | Minimum return or contract value | In the Event of Death
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	$ 19,949,435	$ 20,008,013
Net amount at risk	$ 1,272,073	$ 1,423,229
Average attained age of contractholders	71 years	70 years
Annuity Contracts | Minimum return or contract value | At Annuitization / Accumulation
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	$ 114,832,594	$ 111,734,329
Net amount at risk	$ 2,042,199	$ 2,214,835
Average attained age of contractholders	68 years	68 years
Average period remaining until earliest expected annuitization	0 years	0 years
Variable Life, Variable Universal Life and Universal Life Contracts
Net Amount at Risk by Product and Guarantee [Line Items]
Separate account value	$ 4,087,733	$ 3,781,929
Variable Life, Variable Universal Life and Universal Life Contracts | In the Event of Death
Net Amount at Risk by Product and Guarantee [Line Items]
General account value	9,920,732	9,169,757
Net amount at risk	$ 146,158,176	$ 147,370,237
Average attained age of contractholders	56 years	55 years