Leases Leases (Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019
Leases [Abstract]
Finance leases, Total right-of-use assets	$ 284
Short-term debt	18
Other accruals	259
Finance leases, Total lease liabilities	277
Operating leases, Total right-of-use assets	1,312	$ 1,415
Other accruals	455
Other liabilities and deferred credits	806
Operating leases, Total lease liabilities	$ 1,261	$ 1,415