Other Financial Information - Other Current Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Self-insurance	$ 12	$ 11
Legal and tax reserves	13	31
Other	20	15
Total other current liabilities	$ 45	$ 57

Amount of expenses incurred but not yet paid classified as other, due within one year or the normal operating cycle, if longer.

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