Equity, Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Changes in Accumulated Other Comprehensive Loss, By Component
Beginning balance, accumulated other comprehensive loss, net of tax	$ 20,024
Ending balance, accumulated other comprehensive loss, net of tax	20,370
Accumulated Other Comprehensive Loss [Member]
Changes in Accumulated Other Comprehensive Loss, By Component
Beginning balance, accumulated other comprehensive loss, net of tax	(1,410)	$ (933)
Other comprehensive income (loss) before reclassifications	509	(190)
Amounts reclassified from accumulated other comprehensive loss	8	3
Net other comprehensive income (loss)	517	(187)
Ending balance, accumulated other comprehensive loss, net of tax	(893)	(1,120)
Foreign Currency Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Loss, By Component
Beginning balance, accumulated other comprehensive loss, net of tax	(1,021)	(605)
Other comprehensive income (loss) before reclassifications	509	(198)
Amounts reclassified from accumulated other comprehensive loss	0	0
Net other comprehensive income (loss)	509	(198)
Ending balance, accumulated other comprehensive loss, net of tax	(512)	(803)
Defined Benefit Plans Items [Member]
Changes in Accumulated Other Comprehensive Loss, By Component
Beginning balance, accumulated other comprehensive loss, net of tax	(389)	(328)
Other comprehensive income (loss) before reclassifications	0	8
Amounts reclassified from accumulated other comprehensive loss	8	3
Net other comprehensive income (loss)	8	11
Ending balance, accumulated other comprehensive loss, net of tax	$ (381)	$ (317)