Agreements and Transactions with Affiliates - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating Expense
Related Party Transaction [Line Items]
Labor and related expense	$ 38	$ 50	$ 82	$ 99
General and Administrative Expense
Related Party Transaction [Line Items]
Labor and related expense	35	44	70	91
Restructuring costs
Related Party Transaction [Line Items]
Labor and related expense	$ 9	$ 9	$ 9	$ 9