SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Summary of Significant Accounting Policies - Other Current Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Liabilities, Current [Abstract]
Accrued Capital Expenditures	$ 11	$ 15	$ 21
Other current liabilities	$ 53	$ 61