Fair value measurements Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 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, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0				0
Guaranteed Minimum Income Benefit [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Reported liabilities	$ 815		497		$ 815		497		$ 741	$ 861	$ 529	$ 550
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - Beginning of Period, Liabilities	338		167		452		204
Balance - End of Period, Liabilities	403		125		403		125
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	338	[1]	167	[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	65		(42)		(49)		(79)
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	403	[1],[3]	125	[2],[4]	403	[1],[3]	125	[2],[4]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 65		$ (42)		$ (49)		$ (79)

[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 $815 million at June 30, 2019, and $741 million at March 31, 2019, which includes a fair value derivative adjustment of $403 million and $338 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 $497 million at June 30, 2018, and $529 million at March 31, 2018, which includes a fair value derivative adjustment of $125 million and $167 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 $815 million at June 30, 2019, and $861 million at December 31, 2018, which includes a fair value derivative adjustment of $403 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 $497 million at June 30, 2018, and $550 million at December 31, 2017, which includes a fair value derivative adjustment of $125 million and $204 million, respectively.