Revenue from Contracts with Customers - Contract Assets Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Capitalized Cost To Fulfill Customer Contracts
Change in Capitalized Contract Costs
Balance at beginning of period	$ 229	$ 236	$ 335	$ 329
Additions	274	336	592	682
Amortization	(313)	(357)	(729)	(796)
Impairment	0	0	0	0
Foreign currency translation and other	3	1	(5)	1
Balance at end of period	193	216	193	216
Capitalized Cost To Obtain Customer Contracts
Change in Capitalized Contract Costs
Balance at beginning of period	167	155	171	156
Additions	16	17	28	26
Amortization	(11)	(11)	(23)	(22)
Impairment	0	0	0	0
Foreign currency translation and other	0	0	(4)	1
Balance at end of period	$ 172	$ 161	$ 172	$ 161