Fair value measurements Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - Guaranteed Minimum Income Benefit [Member] - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019		Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Guaranteed Benefit Liability, Net		$ 1,318		$ 935		$ 1,318		$ 935		$ 1,372	$ 897	$ 815	$ 861
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - Beginning of Period, Liabilities		928		403		456		452
Balance - End of Period, Liabilities		882		509		882		509
Guarantees [Member] | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - Beginning of Period, Liabilities		928	[1]	403	[2]	456		452	[2]
Transfers into level 3, liability		0		0		0		0
Transfers out of Level 3, Liabilities		0				0		0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities		0		0		0		0
Net Realized Gains/Losses, Liabilities		(46)	[1]	106	[2]	426		57	[2]
Purchases, Liabilities		0		0		0		0
Sales, Liabilities		0		0		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements		0		0		0		0
Balance - End of Period, Liabilities	[2]	882	[1]	509		882	[1]	509
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)		$ (46)	[1]	$ 106	[2]	$ 426		$ 57	[2]

[1] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Excluded from the table above is the portion of the GLB derivative liability classified as Future policy benefits in the Consolidated balance sheets. The liability for GLB reinsurance was $1,318 million at September 30, 2020, and $1,372 million at June 30, 2020, which includes a fair value derivative adjustment of $882 million and $928 million, respectivel

[2] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Excluded from the table above is the portion of the GLB derivative liability classified as Future policy benefits in the Consolidated balance sheets. The liability for GLB reinsurance was $935 million at September 30, 2019, and $815 million at June 30, 2019, which includes a fair value derivative adjustment of $509 million and $403 million, respectively