Debt and Interest Expense - Anadarko Additional Information (Detail) (USD $)						3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Fair Value Inputs Level 1 and Level 2 [Member] Market Approach Valuation Technique [Member]	Dec. 31, 2012 Fair Value Inputs Level 1 and Level 2 [Member] Market Approach Valuation Technique [Member]	Mar. 31, 2013 Five Billion Dollar Facility [Member]	Mar. 31, 2013 Senior Notes, 7 Point 625 Percent, Due 2014 [Member]	Mar. 31, 2013 Senior Notes, Zero Coupon due 2036 [Member]	Mar. 31, 2013 Senior Notes, Zero Coupon due 2036, Accreted Value [Member]
Debt Instrument [Line Items]
Five billion dollar facility					$ 5,000,000,000
Debt instrument, principal amount	15,337,000,000	14,952,000,000				500,000,000
Debt instrument, stated interest rate						7.625%
Debt instrument, maturity date						Mar. 15, 2014	Oct. 10, 2036
Debt instrument, earliest call date								Oct. 10, 2013
Total borrowings, fair value			$ 16,500,000,000	$ 16,200,000,000