Receivables, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Receivables, Net
Trade accounts receivable	$ 647	$ 812
Unbilled receivables	556	478
Less allowances for doubtful accounts	(17)	(10)
Net trade accounts receivable	1,186	1,280
Other receivables	445	522
Receivables, net	1,631	1,802
Net accounts receivable under long-term contracts, due primarily from agencies of the U.S. government and their prime contractors	247	240
Recognized sales value of performance not yet billable	$ 164	164
Average length of long-term contracts	2 years 9 months
Average remaining length of contracts	1 year
Net receivables expected to be collected within one year	$ 247
Maximum available sale of the accounts receivables under factoring program	1,400	1,200
Amount of accounts receivable available for sale under the factoring program	$ 230	$ 178