Derivative contracts (Detail) - Finance and Financial Products [Member] - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Liabilities		$ 2,890	$ 3,836
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Liabilities		2,890	3,836
Not Designated as Hedging Instrument [Member] | Equity Index Put Options [Member]
Derivative [Line Items]
Liabilities		2,890	3,552
Notional Value	[1]	$ 26,497	27,722
Not Designated as Hedging Instrument [Member] | Credit Default [Member]
Derivative [Line Items]
Liabilities	[2]		284
Notional Value	[2]		$ 7,792

[1] Represents the aggregate undiscounted amounts payable assuming that the value of each index is zero at each contract's expiration date. Certain of these contracts are denominated in foreign currencies. Notional amounts are based on the foreign currency exchange rates as of each balance sheet date.

[2] In July 2016, our remaining credit default contract was terminated by mutual agreement with the counterparty. We no longer have any exposure to losses under credit default contracts.