Revenue Recognition - Capitalized Contract Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Acquisition Costs
Capitalized Contract Cost [Roll Forward]
Beginning of period balance	$ 86	$ 74	$ 79	$ 64
Costs incurred	7	11	30	29
Amortization	(16)	(12)	(32)	(20)
End of period balance	77	73	77	73
Fulfillment Costs
Capitalized Contract Cost [Roll Forward]
Beginning of period balance	122	97	121	84
Costs incurred	21	25	44	51
Amortization	(21)	(16)	(43)	(29)
End of period balance	$ 122	$ 106	$ 122	$ 106