Discontinued Operations - Schedule of Discontinued Operations Reflected in Consolidated Condensed Statements of Income (Parenthetical) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2014 USD ($)
HighMount [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax benefit on impairment loss	$ 62
CAC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on sale, tax benefit	$ 40