Equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 17,231	$ 16,985	$ 15,775
Impact of adoption of ASU 2018-02		0
Other comprehensive income (loss)	72	(92)	121
Ending balance	17,286	17,231	16,985
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(227)	(136)	(345)
Other comprehensive income (loss)	51	(91)	203
Impact of adoption of ASU 2018-02		(1)
Income tax benefit (expense)	(1)	1	6
Other comprehensive income (loss)	50	(91)	209
Ending balance	(177)	(227)	(136)
Comprehensive income from equity method investment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	2	2	2
Other comprehensive income (loss)	(1)	0	0
Impact of adoption of ASU 2018-02		0
Income tax benefit (expense)	0	0	0
Other comprehensive income (loss)	(1)	0	0
Ending balance	1	2	2
Employee benefit plans adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(90)	(89)	(109)
Other comprehensive income (loss)	32	33	28
Impact of adoption of ASU 2018-02		(25)
Income tax benefit (expense)	(9)	(9)	(8)
Other comprehensive income (loss)	23	(1)	20
Ending balance	(67)	(90)	(89)
Fair value of available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	0	0	108
Other comprehensive income (loss)	0	0	(108)
Impact of adoption of ASU 2018-02		0
Income tax benefit (expense)	0	0	0
Other comprehensive income (loss)	0	0	(108)
Ending balance	0	0	0
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(315)	(223)	(344)
Other comprehensive income (loss)	82	(58)	123
Impact of adoption of ASU 2018-02		(26)
Income tax benefit (expense)	(10)	(8)	(2)
Other comprehensive income (loss)	72	(92)	121
Ending balance	$ (243)	$ (315)	$ (223)