Finance Receivables - Activity in post-acquisition consumer finance receivables portfolio (Details) (Consumer Finance Receivables [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts Notes And Loans Receivable Rollforward [Roll Forward]
Balance at end of period	$ 25,623	$ 23,130
International Segment [Member]
Accounts Notes And Loans Receivable Rollforward [Roll Forward]
Balance at end of period	12,262	11,742
North America Segment [Member]
Accounts Notes And Loans Receivable Rollforward [Roll Forward]
Balance at end of period	13,361	11,388
Post-Acquisition Portfolio [Member]
Accounts Notes And Loans Receivable Rollforward [Roll Forward]
Balance at beginning of period	21,956	8,831
International operations acquisition		9,709
Loans purchased	15,085	9,597
Charge-offs	(914)	(638)
Principal collections and other	(9,555)	(5,697)
Change in carrying value adjustment	0	14
Foreign currency translation	(1,408)	140
Balance at end of period	25,164	21,956
Post-Acquisition Portfolio [Member] | International Segment [Member]
Accounts Notes And Loans Receivable Rollforward [Roll Forward]
Balance at beginning of period	11,394	0
International operations acquisition		9,709
Loans purchased	8,277	4,471
Charge-offs	(138)	(54)
Principal collections and other	(6,014)	(2,886)
Change in carrying value adjustment	0	14
Foreign currency translation	(1,403)	140
Balance at end of period	12,116	11,394
Post-Acquisition Portfolio [Member] | North America Segment [Member]
Accounts Notes And Loans Receivable Rollforward [Roll Forward]
Balance at beginning of period	10,562	8,831	5,314
International operations acquisition		0	0
Loans purchased	6,808	5,126	5,579
Charge-offs	(776)	(584)	(304)
Principal collections and other	(3,541)	(2,811)	(1,758)
Change in carrying value adjustment	0	0	0
Foreign currency translation	(5)	0	0
Balance at end of period	$ 13,048	$ 10,562	$ 8,831