Reserves for Losses (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance, January 1			$ 573	$ 521
Provisions	$ 224	$ 245	477	487
Net write-offs			(426)	(435)
Other			(8)	(15)
Balance, June 30	$ 616	$ 558	616	558
Recoveries			184	178
Troubled Debt Restructuring [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Net write-offs			(6)
Recoveries				2
Foreign Currency Translation Adjustments [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Other			3	(1)
Other Items [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Other			$ (11)	$ (14)