Derivative Instruments and Hedging Activities - Commodity Derivative Activity Recorded in Statement of Consolidated Operations (Detail) - Other Revenue [Member] - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Realized loss	$ 0	$ 0	$ (16)
Unrealized gain (loss)	0	0	300
Gain (loss) on derivatives not designated as cash flow hedges	$ 0	$ 0	$ 284