Assets and Liabilities of Business Held for Sale - Assets and Liabilities Held for Sale (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts receivable, net	$ 576	$ 521
Investments	8,300	7,700
Total assets of business held for sale	10,022	9,512
Insurance and contractholder liabilities	6,591	6,308
Total liabilities of business held for sale	7,195	6,812
Group Disability and Life | Held-for-Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents	798	743
Accounts receivable, net	576	521
Investments	8,258	7,709
Other assets	390	539
Total assets of business held for sale	10,022	9,512
Insurance and contractholder liabilities	6,591	6,308
Other liabilities	604	504
Total liabilities of business held for sale	$ 7,195	$ 6,812