Summary of Significant Accounting Policies (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Mar. 31, 2015
Schedule Of Significant Accounting Policies [Line Items]
Asset Impairment Charges and Unproved Oil and Gas Leasehold Impairments			$ 281	$ 2,700
Asset impairments				2,600
Impairment of GTP assets			105
Oil and gas property, fair value disclosure	$ 143	$ 516	143	516		$ 1,200
Impairment of goodwill				163
Oil and Gas Properties, Proved [Member]
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments	68	349	68	2,261
Oil and Gas Properties, Unproved [Member]
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments	66	$ 148	108	$ 316
US and Canada [Member]
Schedule Of Significant Accounting Policies [Line Items]
Asset impairments			176
Egypt [Member]
Schedule Of Significant Accounting Policies [Line Items]
Goodwill	$ 87		$ 87		$ 87