Fair value measurements Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2019		Sep. 30, 2018		Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Derivative Financial Instruments, Liabilities [Member] | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - Beginning of Period, Liabilities			$ 2				$ 2
Transfers into level 3, liability			0				0
Transfers out of Level 3, Liabilities			0				0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities			0				0
Net Realized Gains/Losses, Liabilities			0				0
Purchases, Liabilities			0				0
Sales, Liabilities			0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements			0				0
Balance - End of Period, Liabilities			2				2
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)			0				0
Guaranteed Minimum Income Benefit [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Guaranteed Benefit Liability, Net	$ 935		453		$ 935		453		$ 815	$ 861	$ 497	$ 550
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - Beginning of Period, Liabilities	403		125		452		204
Balance - End of Period, Liabilities	509		71		509		71
Guaranteed Minimum Income Benefit [Member] | Guarantees [Member] | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - Beginning of Period, Liabilities	403	[1]	125	[2]	452	[3]	204	[4]
Transfers into level 3, liability	0		0		0		0
Transfers out of Level 3, Liabilities	0		0		0		0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities	0		0		0		0
Net Realized Gains/Losses, Liabilities	106		(54)		57		(133)
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	509	[1],[3]	71	[2],[4]	509	[1],[3]	71	[2],[4]
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 106		$ (54)		$ 57		$ (133)

[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 $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

[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 $453 million at September 30, 2018, and $497 million at June 30, 2018, which includes a fair value derivative adjustment of $71 million and $125 million, respectively.

[3] 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 $861 million at December 31, 2018, which includes a fair value derivative adjustment of $509 million and $452 million, respectively.

[4] 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 $453 million at September 30, 2018, and $550 million at December 31, 2017, which includes a fair value derivative adjustment of $71 million and $204 million, respectively.