Supplemental Quarterly Financial Data - Supplemental Quarterly Financial Data (Parenthetical) (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Write-down of the carrying value of Oil and Gas properties, net of tax		$ 16,620,000,000	$ 3,068,000,000	$ 541,000,000
Asset impairments total	$ 604,000,000	1,920,000,000	1,919,000,000	$ 0
Impairment of goodwill			1,300,000,000
Impairment of assets held for sale and other assets			$ 604,000,000
Inventory write-downs		55,000,000
Impairment of gathering, transmission, and processing (GTP) facilities		1,700,000,000
Impairment of equity method investment		$ 148,000,000