Interim Consolidated Financial Statements (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of changes in accounting principle	$ 1	$ 2
Trade Accounts Receivable
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of changes in accounting principle	(1)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of changes in accounting principle	$ 1	$ 2