Accounts Payable and Other Current Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts Payable and Other Current Liabilities [Abstract]
Accounts payable	$ 396	$ 359
Accrued sales and use taxes	307	218
Accrued marketing and commissions, current	223	190
Employee-related Liabilities, Current	188	176
Deferred Revenue, Current	161	135
Public liability and property damage insurance liabilities, current	144	145
Accrued Insurance, Current	117	103
Other	349	293
Accounts payable and other current liabilities	$ 1,885	$ 1,619