Discontinued Operations-Downstream Businesses - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Sep. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Income Statement by Disposal Groups, Including Discontinued Operations [Line Items]
Refined petroleum products and natural gas			$ 1,362
Less: Last-in, first-out (LIFO) adjustment			1,123
Other inventories	361		527
Effect of LIFO inventory liquidation following the cessation of refining operations at the Port Reading facility, pre-tax gain in the first quarter of 2013 and in conjunction with the Corporation's ongoing divestiture program in the third quarter of 2013	228	218
Effect of LIFO inventory liquidation following the cessation of refining operations at the Port Reading facility, after income taxes in the first quarter of 2013 and in conjunction with the Corporation's ongoing divestiture program in the third quarter of 2013	143	137
Additional depreciation due to the cessation of refining operations at the Port Reading facility		80
Discontinued Downstream Businesses [Member]
Income Statement by Disposal Groups, Including Discontinued Operations [Line Items]
Refined petroleum products and natural gas	1,040
Less: Last-in, first-out (LIFO) adjustment	689
Other inventories	$ 118