Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Summary Of Significant Accounting Policies [Line Items]
Gains (losses) on derivative and hedging activities, net	$ (32)	$ (40)	$ (25)	$ 8
ASC 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Lease assets and liabilities amount			28
ASU 2017-12 [Member] | Interest Expense [Member]
Summary Of Significant Accounting Policies [Line Items]
Gains (losses) on derivative and hedging activities, net	$ 7		$ 9