Discontinued Operations - Summary of Sales and Other Operating Revenues and Income from Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (loss) from discontinued operations, net of income taxes	$ 682	$ 1,186	$ 255
Less: Net income (loss) attributable to noncontrolling interests	57	(6)	20
Income from discontinued operations, net of income taxes	625	1,192	235
Discontinued Operations [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Sales and other operating revenues	9,576	22,652	25,517
Income from discontinued operations before income taxes	1,071	1,835	400
Current tax provision (benefit)			7	[1]
Deferred tax provision (benefit)	389	649	138
Provision for income taxes, discontinued operations	$ 389	$ 649	$ 145

[1] Substantially all current tax expense relates to foreign taxes on energy trading operations.