Schedule of Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 2,032	$ 2,747	$ 1,990
Charged to costs and expenses	458	35	1,125
Deductions	606	750	368
Balance at end of period	1,884	2,032	2,747
Credit losses [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	592	608	503
Charged to costs and expenses	310	419	476
Deductions	372	435	371
Balance at end of period	530	592	608
Doubtful receivables [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	94	404	377
Charged to costs and expenses	18	5	24
Deductions	63	315	(3)
Balance at end of period	49	94	404
Inventories (primarily service part obsolescence) [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	373	243	201
Charged to costs and expenses	89	130	42
Deductions	0	0	0
Balance at end of period	462	373	243
Deferred tax assets [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	973	1,492	909
Charged to costs and expenses	41	(519)	583
Deductions	171	0	0
Balance at end of period	843	973	1,492
Valuation Allowance Of Deferred Tax Assets Recognized In Accumulated Other Comprehensive Income Loss [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Charged to costs and expenses	(78)	(101)	127
Valuation Allowance of Deferred Tax Assets Recognized in Income Statement [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Charged to costs and expenses	$ (52)	$ (418)	$ 456