Revenue - Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Contract Assets (Unearned Income)
Current contract assets	$ 169		$ 155
Long-term contract assets	8		10
Current unearned income	(109)		(108)
Long-term unearned income	(19)		(21)
Net Contract Assets (Unearned Income)	49		36
Accounts receivable, net	690		$ 652
Revenue recognized	$ 42	$ 53

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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