Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Term To Charge Off Finance Receivables									greater than 120 days past due
Number Of Days At Which Finance Receivables Impaired									when an account is deemed to be uncollectible or when an account is 120 days delinquent
Allowance for credit losses, finance receivables
Beginning balance				$ 484				$ 373	$ 484	$ 373
Charge-offs									(517)	(443)
Recoveries									148	122
Provision for credit losses									469	438
Other									13	(6)
Ending balance	$ 597				$ 484				597	484	$ 373
Analysis of ending balance of allowance for credit losses, finance receivables
Collective impairment allowance	573				463				573	463
Specific impairment allowance	24				21				24	21
Ending balance	597				484				597	484	373
Analysis of ending balance of finance receivables
Collectively evaluated for impairment	116,076				102,991				116,076	102,991
Specifically evaluated for impairment	524				474				524	474
Financing Receivables	116,600				103,465				116,600	103,465
Allowance for credit losses, net investment in operating leases
Beginning balance				64				49	64	49
Charge-offs									(208)	(175)
Recoveries									96	81
Other									0	0
Ending balance	71				64				71	64	49
Analysis of ending balance of allowance for credit losses, net investment in operating leases
Collective impairment allowance	71				64				71	64
Specific impairment allowance	0				0				0	0
Ending balance	71				64				71	64	49
Analysis of ending balance of net investment in operating leases
Collectively evaluated for impairment	26,732				27,273				26,732	27,273
Individually evaluated for impairment	0				0				0	0
Net investment in operating leases before allowance for credit losses	26,732				27,273				26,732	27,273
Total allowance
Beginning balance				548				422	548	422
Charge-offs									(725)	(618)
Recoveries									244	203
Provision for credit losses	168	$ 169	$ 99	152	144	$ 138	$ 137	128	588	547	347
Other									13	(6)
Ending balance	668				548				668	548	422
Analysis of Ending Balance of Finance Receivables and Net Investment in Operating Leases [Abstract]
Collective impairment allowance	644				527				644	527
Specific impairment allowance	24				21				24	21
Ending balance	668				548				668	548	422
Ending balance, net of allowance for credit losses	116,003				102,981				116,003	102,981
Ending balance, net investment in operating leases	26,661				27,209				26,661	27,209
Net Investment in Operating Leases [Member]
Allowance for credit losses, finance receivables
Provision for credit losses									119	109
Consumer Segment [Member]
Allowance for credit losses, finance receivables
Beginning balance				469				357	469	357
Charge-offs									(510)	(435)
Recoveries									139	116
Provision for credit losses									471	436
Other									13	(5)
Ending balance	582				469				582	469	357
Analysis of ending balance of allowance for credit losses, finance receivables
Collective impairment allowance	560				450				560	450
Specific impairment allowance	22				19				22	19
Ending balance	582				469				582	469	357
Analysis of ending balance of finance receivables
Collectively evaluated for impairment	74,801				64,971				74,801	64,971
Specifically evaluated for impairment	386				367				386	367
Financing Receivables	75,187				65,338				75,187	65,338
Analysis of Ending Balance of Finance Receivables and Net Investment in Operating Leases [Abstract]
Ending balance, net of allowance for credit losses	74,605				64,869				74,605	64,869
Non-Consumer Segment [Member]
Allowance for credit losses, finance receivables
Beginning balance				$ 15				$ 16	15	16
Charge-offs									(7)	(8)
Recoveries									9	6
Provision for credit losses									(2)	2
Other									0	(1)
Ending balance	15				15				15	15	16
Analysis of ending balance of allowance for credit losses, finance receivables
Collective impairment allowance	13				13				13	13
Specific impairment allowance	2				2				2	2
Ending balance	15				15				15	15	$ 16
Analysis of ending balance of finance receivables
Collectively evaluated for impairment	41,275				38,020				41,275	38,020
Specifically evaluated for impairment	138				107				138	107
Financing Receivables	41,413				38,127				41,413	38,127
Analysis of Ending Balance of Finance Receivables and Net Investment in Operating Leases [Abstract]
Ending balance, net of allowance for credit losses	$ 41,398				$ 38,112				$ 41,398	$ 38,112