Other Financial Statement Items - Accounts Receivable and Unbilled Revenue (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Trade receivables and unbilled revenues	$ 1,150	$ 1,151
Allowance for credit losses	(73)	(69)	$ (66)	$ (62)
Accounts receivable and unbilled revenues, net	$ 1,077	$ 1,082