Certain Long-Duration Contracts with Guarantees (Variable Annuity Contracts) (Details) - Annuity Contracts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Return of net deposits | In the Event of Death
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	$ 122,530,558	$ 120,240,930
Net amount at risk	$ 203,506	$ 229,080
Average attained age of contractholders	69 years	68 years
Minimum return or contract value | In the Event of Death
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	$ 23,359,093	$ 23,563,604
Net amount at risk	$ 2,020,533	$ 2,254,621
Average attained age of contractholders	71 years	70 years
Minimum return or contract value | At Annuitization / Accumulation
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	$ 131,888,370	$ 129,812,105
Net amount at risk	$ 3,702,796	$ 3,989,437
Average attained age of contractholders	70 years	69 years
Average period remaining until earliest expected annuitization	0 years	0 years