|12 Months Ended|
Dec. 31, 2018
|Accrued Liabilities, Current [Abstract]|
As of December 31, 2018 and 2017, accrued liabilities consisted of the following (in millions):
The entire disclosure for accounts payable and accrued liabilities at the end of the reporting period.
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef