Supplemental Schedule of Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums, Life Insurance in Force	$ 1,990.0	$ 1,316.0	$ 1,363.0
Ceded Premiums, Life Insurance in Force	184,625.0	192,864.0	186,172.0
Assumed Premiums, Life Insurance in Force	3,480,692.0	3,480,206.0	3,329,181.0
Premiums, Net, Life Insurance in Force	$ 3,298,057.0	$ 3,288,658.0	$ 3,144,372.0
Life Insurance in Force Premiums, Percentage Assumed to Net	105.50%	105.80%	105.90%
Direct Premiums Earned	$ 58.0	$ 76.0	$ 63.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	947.0	929.0	860.0
Assumed Premiums Earned	12,583.0	12,150.0	11,341.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 11,694.0	$ 11,297.0	$ 10,544.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	107.60%	107.50%	107.60%
US Traditional Segment Reporting Information [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Earned	$ 23.0	$ 29.0	$ 32.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	585.0	591.0	593.0
Assumed Premiums Earned	6,399.0	6,291.0	6,095.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 5,837.0	$ 5,729.0	$ 5,534.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	109.60%	109.80%	110.20%
US Non-Traditional Segment Reporting Information [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Earned	$ 3.0	$ 2.0	$ 5.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	0.0	0.0	0.0
Assumed Premiums Earned	50.0	37.0	22.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 53.0	$ 39.0	$ 27.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	94.30%	95.40%	82.70%
Canada Traditional Segment Reporting Information [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Earned	$ 0.0	$ 0.0	$ 0.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	54.0	54.0	47.0
Assumed Premiums Earned	1,106.0	1,120.0	1,071.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 1,052.0	$ 1,066.0	$ 1,024.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	105.10%	105.00%	104.60%
Canada Non-Traditional Segment Reporting Information [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Earned	$ 0.0	$ 0.0	$ 0.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	0.0	0.0	0.0
Assumed Premiums Earned	83.0	89.0	43.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 83.0	$ 89.0	$ 43.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	100.00%	100.00%	100.00%
EMEA Traditional Segment Reporting Information [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Earned	$ 32.0	$ 45.0	$ 26.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	24.0	52.0	26.0
Assumed Premiums Earned	1,548.0	1,449.0	1,424.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 1,556.0	$ 1,442.0	$ 1,424.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	99.50%	100.60%	100.00%
EMEA Non-Traditional Segment Reporting Information [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Earned	$ 0.0	$ 0.0	$ 0.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	178.0	148.0	144.0
Assumed Premiums Earned	430.0	366.0	339.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 252.0	$ 218.0	$ 195.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	170.60%	167.90%	173.50%
Asia Pacific Traditional Segment Reporting Information [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Earned	$ 0.0	$ 0.0	$ 0.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	106.0	84.0	50.0
Assumed Premiums Earned	2,787.0	2,652.0	2,346.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 2,681.0	$ 2,568.0	$ 2,296.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	104.00%	103.20%	102.20%
Asia Pacific Non-Traditional Segment Reporting Information [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Earned	$ 0.0	$ 0.0	$ 0.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	0.0	0.0	0.0
Assumed Premiums Earned	180.0	146.0	1.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 180.0	$ 146.0	$ 1.0
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	100.00%	100.00%	100.00%