Finance Receivables - Commercial Finance Receivables (Details) - Commercial Finance Receivables [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts Notes And Loans Receivable Rollforward [Roll Forward]
Balance at beginning of period	$ 7,880	$ 5,392	$ 4,884
Net funding	2,356	2,534	848
Charge-offs	(2)	(1)	(3)
Foreign currency translation	78	(45)	(337)
Balance at end of period	$ 10,312	$ 7,880	$ 5,392