Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and Qualifying Accounts Beginning Balance		$ 174	$ 192	$ 213
Additions charged to bad debt provision	[1]	33	37	49
Amounts (credited) charged to other income statement accounts	[1]	13	6	5
Deductions and other, net of recoveries	[2]	(53)	(61)	(75)
Valuation and Qualifying Accounts Ending Balance		167	174	192
Accounts Receivable
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and Qualifying Accounts Beginning Balance		64	74	82
Additions charged to bad debt provision	[1]	16	13	21
Amounts (credited) charged to other income statement accounts	[1]	(2)	2	5
Deductions and other, net of recoveries	[2]	(19)	(25)	(34)
Valuation and Qualifying Accounts Ending Balance		59	64	74
Finance Receivables
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and Qualifying Accounts Beginning Balance		110	118	131
Additions charged to bad debt provision	[1]	17	24	28
Amounts (credited) charged to other income statement accounts	[1]	15	4	0
Deductions and other, net of recoveries	[2]	(34)	(36)	(41)
Valuation and Qualifying Accounts Ending Balance		$ 108	$ 110	$ 118

[1] Bad debt provisions relate to estimated losses due to credit and similar collectability issues. Other charges (credits) relate to adjustments to reserves necessary to reflect events of non-payment such as customer accommodations and contract terminations.

[2] Deductions and other, net of recoveries primarily relates to receivable write-offs, but also includes the impact of foreign currency translation adjustments and recoveries of previously written off receivables.