Equity, Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in Accumulated Other Comprehensive Income (Loss) by Component, Net of Tax
Beginning balance, accumulated other comprehensive income (loss), net of tax	$ 21,991
Other comprehensive income (loss) before reclassifications	(508)	$ 458	$ (484)
Amounts reclassified from accumulated other comprehensive loss	32	12	7
Other comprehensive income (loss)	(476)	470	(477)
Reclassification of stranded income tax effects of Tax Reform to retained earnings per ASU 2018-02 (see Note 1)	0
Ending balance, accumulated other comprehensive income (loss), net of tax	21,667	21,991
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component, Net of Tax
Beginning balance, accumulated other comprehensive income (loss), net of tax	(940)	(1,410)	(933)
Reclassification of stranded income tax effects of Tax Reform to retained earnings per ASU 2018-02 (see Note 1)	(91)
Ending balance, accumulated other comprehensive income (loss), net of tax	(1,507)	(940)	(1,410)
Foreign Currency Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component, Net of Tax
Beginning balance, accumulated other comprehensive income (loss), net of tax	(507)	(1,021)	(605)
Other comprehensive income (loss) before reclassifications	(515)	514	(416)
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Other comprehensive income (loss)	(515)	514	(416)
Reclassification of stranded income tax effects of Tax Reform to retained earnings per ASU 2018-02 (see Note 1)	0
Ending balance, accumulated other comprehensive income (loss), net of tax	(1,022)	(507)	(1,021)
Defined Benefit Plan Items Adjustment [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component, Net of Tax
Beginning balance, accumulated other comprehensive income (loss), net of tax	(433)	(389)	(328)
Other comprehensive income (loss) before reclassifications	7	(56)	(68)
Amounts reclassified from accumulated other comprehensive loss	32	12	7
Other comprehensive income (loss)	39	(44)	(61)
Reclassification of stranded income tax effects of Tax Reform to retained earnings per ASU 2018-02 (see Note 1)	(91)
Ending balance, accumulated other comprehensive income (loss), net of tax	$ (485)	$ (433)	$ (389)