Summary of Information about Contract Balances with Customers (Detail) - USD ($) $ in Millions		Jun. 30, 2018		Mar. 31, 2018	Dec. 31, 2017
Contract With Customer Asset And Liability [Abstract]
Receivables, net		$ 439			$ 460
Contract assets	[2]	$ 7	[1]	$ 8

[1] Included in prepaid expenses and contract assets

[2] The contract asset is determined at each period end, this table reflects the rollforward of the period end balance.