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, 2019	Dec. 31, 2018
Annuity Contracts | Return of net deposits | In the Event of Death
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	$ 101,413,706	$ 87,412,536
Net amount at risk	$ 23,061	$ 656,027
Average attained age of contractholders	67 years	66 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	$ 20,008,013	$ 18,574,416
Net amount at risk	$ 1,423,229	$ 3,186,237
Average attained age of contractholders	70 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	$ 111,734,329	$ 97,055,710
Net amount at risk	$ 2,214,835	$ 4,510,250
Average attained age of contractholders	68 years	67 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	$ 3,781,929	$ 3,301,084
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	9,169,757	8,224,464
Net amount at risk	$ 147,370,237	$ 144,225,578
Average attained age of contractholders	55 years	55 years