Revenue Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2018
Revenue from Contract with Customer [Abstract]
Operating-type lease and sales-type lease, revenues	$ 402
Revenue, remaining performance obligation	$ 1,900
Revenue, remaining performance obligation, expected satisfaction in the next 12 months, percent	43.00%
Revenue, remaining performance obligation, expected satisfaction in year two, percent	27.00%
Contract with customer, asset, net	$ 82	$ 114
Contract with customer, liability	799	$ 783
Contract with customer, liability, revenue recognized	$ 657