Fair value measurements Fair Value Measurements (Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Guaranteed Minimum Income Benefit
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance - Beginning of year, liabilities		$ 609	[1],[2]	$ 406	[2],[3]	$ 193	[3]
Transfers Into Level 3, liabilities		0	[1]	0	[2]	0	[3]
Transfers out of Level 3, liabilities	[3]					0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities		0	[1]	0	[2]
Net Realized Gains/Losses, Liabilities		(50)	[1]	203	[2]	213	[3]
Purchased, liabilities		0	[1]	0	[2]	0	[3]
Sales, liabilities		0	[1]	0	[2]	0	[3]
Settlements, liabilities		0	[1]	0	[2]	0	[3]
Balance - End of year, liabilities		559	[1]	609	[1],[2]	406	[2],[3]
GLB liability		853		888		663		$ 427
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities		(50)	[1]	203	[2]	213	[3]
Other Derivative Instruments Fair Value [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance - Beginning of year, liabilities		6		4		0
Transfers Into Level 3, liabilities		0		0		2
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities		0
Net Realized Gains/Losses, Liabilities		5		2		2
Purchased, liabilities		2		0		0
Sales, liabilities		0		0
Settlements, liabilities		0		0
Balance - End of year, liabilities		13		6		4
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities		$ 5		$ 2		$ 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. Refer to Note 5 c) for additional information.

[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 $888 million at December 31, 2015 and $663 million at December 31, 2014, which includes a fair value derivative adjustment of $609 million and $406 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 $663 million at December 31, 2014 and $427 million at December 31, 2013, which includes a fair value derivative adjustment of $406 million and $193 million, respectively.