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, 2016	Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015		Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Guaranteed Minimum Income Benefit [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Reported liabilities		$ 1,200	$ 1,000		$ 1,200		$ 1,000		$ 888	$ 615	$ 663
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - Beginning of Period, Liabilities	[1]	971	347		609		406
Transfers into level 3, liability		0	0		0		0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities		0	0		0		0
Net Realized Gains/Losses, Liabilities		(88)	397		274		338
Transfers out of Level 3, Liabilities					0
Purchases, Liabilities		0	0		0		0
Sales, Liabilities		0	0		0		0
Settlements, Liabilities		0	0		0		0
Balance - End of Period, Liabilities	[2]	883	744	[1]	883		744	[1]
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities		(88)	397		274	[2]	338	[2]
Guaranteed Minimum Income Benefit [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - Beginning of Period, Liabilities					609
Balance - End of Period, Liabilities	[1]	883			883
Other Derivative Instruments Fair Value [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - Beginning of Period, Liabilities		10	3		6		4
Transfers into level 3, liability			0		0		0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities			0		0		0
Net Realized Gains/Losses, Liabilities		0	4		2		3
Transfers out of Level 3, Liabilities					0
Purchases, Liabilities		0	0		2		0
Sales, Liabilities			0		0		0
Settlements, Liabilities			0		2		0
Balance - End of Period, Liabilities		8	7		8		7
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities		$ 0	$ 4		$ 2		$ 3

[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 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 $1.0 billion at September 30, 2015, and $615 million at June 30, 2015, which includes a fair value derivative adjustment of $744 million and $347 million, respectively. Assets Liabilities Nine Months EndedAvailable-for-Sale Debt Securities EquitysecuritiesShort-term investmentsOtherinvestments OtherderivativeinstrumentsGLB(1)September 30, 2016Foreign Corporatesecurities MBS (in millions of U.S. dollars) Balance–Beginning of Period$57 $174 $53 $16$—$212 $6$609Transfers into Level 39 18 — ——— ——Transfers out of Level 3(2) — — ——— ——Change in Net Unrealized Gains (Losses) included in OCI8 17 — 2—4 ——Net Realized Gains/Losses(6) (12) — 1—— 2274Purchases (2)52 472 1 236222 2—Sales(10) (48) (8) (5)—— ——Settlements(5) (15) — ——(15) (2)—Balance–End of Period$103 $606 $46 $37$62$223 $8$883Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date$(5) $(11) $— $—$—$— $2$274(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 for additional information.(2) Includes acquired invested assets as a result of the Chubb Corp acquisition. Assets LiabilitiesNine Months Ended Available-for-Sale Debt Securities Other investments OtherderivativeinstrumentsGLB(1)September 30, 2015 Foreign Corporatesecurities MBS Equitysecurities (in millions of U.S. dollars) Balance–Beginning of Period $22 $187 $15 $2 $204 $4$406Transfers into Level 3 29 15 — — — ——Change in Net Unrealized Gains (Losses) included in OCI (1) 1 — 2 (7) ——Net Realized Gains/Losses (1) (4) — (2) — 3338Purchases 9 38 41 2 21 ——Sales (1) (10) (1) — — ——Settlements (4) (44) (1) — (9) ——Balance–End of Period $53$183$54 $4$209 $7$744Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $(1) $(2) $— $(2) $— $3$338(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 $1.0 billion at September 30, 2015, and $663 million at December 31, 2014, which includes a fair value derivative adjustment of $744 million and $406 million, respectively.