Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Prepaid expenses and other current assets:
Prepaid expenses	$ 50	$ 50	$ 61
Value added taxes	44	46	42
Other	160	103	131
Prepaid expenses and other current assets	$ 254	$ 199	$ 234