Significant Accounting Policies (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended	7 Months Ended	9 Months Ended
	Jul. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Jul. 31, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Advertising costs		$ 8
Predecessor
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Advertising costs	$ 4		$ 14	$ 33	$ 42