Revenue (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Operating-type lease and sales-type lease, revenues	$ 444	$ 432	$ 401
Revenue, remaining performance obligation	$ 3,000
Revenue, remaining performance obligation, expected satisfaction in the next 12 months, percent	50.00%
Revenue, remaining performance obligation, expected satisfaction in year two, percent	23.00%
Contract with customer, asset, net	$ 65	77
Contract with customer, liability	1,400	806
Contract with customer, liability, revenue recognized	$ 638	$ 603