Accounts Receivable (Accounts Receivable) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Accounts Receivable [Abstract]
Retail and wholesale	$ 680	$ 745
Other	77	83
Less: Allowance for doubtful accounts	(83)	(105)
Accounts receivable, net	$ 674	$ 723

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant