Debt and Interest Expense - Outstanding Debt Table (Detail) (USD $) In Millions, unless otherwise specified						12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2013 5.750% Senior Notes due 2014	Dec. 31, 2012 5.750% Senior Notes due 2014	Dec. 31, 2013 7.625% Senior Notes due 2014	Dec. 31, 2012 7.625% Senior Notes due 2014	Dec. 31, 2013 5.950% Senior Notes due 2016	Dec. 31, 2012 5.950% Senior Notes due 2016	Dec. 31, 2013 6.375% Senior Notes due 2017	Dec. 31, 2012 6.375% Senior Notes due 2017	Dec. 31, 2013 7.050% Debentures due 2018	Dec. 31, 2012 7.050% Debentures due 2018	Dec. 31, 2013 WES 2.600% Senior Notes due 2018 Western Gas Partners, LP [Member]	Dec. 31, 2012 WES 2.600% Senior Notes due 2018 Western Gas Partners, LP [Member]	Dec. 31, 2013 6.950% Senior Notes due 2019	Dec. 31, 2012 6.950% Senior Notes due 2019	Dec. 31, 2013 8.700% Senior Notes due 2019	Dec. 31, 2012 8.700% Senior Notes due 2019	Dec. 31, 2013 WES 5.375% Senior Notes due 2021 Western Gas Partners, LP [Member]	Dec. 31, 2012 WES 5.375% Senior Notes due 2021 Western Gas Partners, LP [Member]	Dec. 31, 2013 WES 4.000% Senior Notes due 2022 Western Gas Partners, LP [Member]	Dec. 31, 2012 WES 4.000% Senior Notes due 2022 Western Gas Partners, LP [Member]	Dec. 31, 2013 6.950% Senior Notes due 2024	Dec. 31, 2012 6.950% Senior Notes due 2024	Dec. 31, 2013 7.500% Debentures due 2026	Dec. 31, 2012 7.500% Debentures due 2026	Dec. 31, 2013 7.000% Debentures due 2027	Dec. 31, 2012 7.000% Debentures due 2027	Dec. 31, 2013 7.125% Debentures due 2027	Dec. 31, 2012 7.125% Debentures due 2027	Dec. 31, 2013 6.625% Debentures due 2028	Dec. 31, 2012 6.625% Debentures due 2028	Dec. 31, 2013 7.150% Debentures due 2028	Dec. 31, 2012 7.150% Debentures due 2028	Dec. 31, 2013 7.200% Debentures due 2029	Dec. 31, 2012 7.200% Debentures due 2029	Dec. 31, 2013 7.950% Debentures due 2029	Dec. 31, 2012 7.950% Debentures due 2029	Dec. 31, 2013 7.500% Senior Notes due 2031	Dec. 31, 2012 7.500% Senior Notes due 2031	Dec. 31, 2013 7.875% Senior Notes due 2031	Dec. 31, 2012 7.875% Senior Notes due 2031	Dec. 31, 2013 Zero-Coupon Senior Notes due 2036	Dec. 31, 2012 Zero-Coupon Senior Notes due 2036	Dec. 31, 2013 6.450% Senior Notes due 2036	Dec. 31, 2012 6.450% Senior Notes due 2036	Dec. 31, 2013 7.950% Senior Notes due 2039	Dec. 31, 2012 7.950% Senior Notes due 2039	Dec. 31, 2013 6.200% Senior Notes due 2040	Dec. 31, 2012 6.200% Senior Notes due 2040	Dec. 31, 2013 7.730% Debentures due 2096	Dec. 31, 2012 7.730% Debentures due 2096	Dec. 31, 2013 7.500% Debentures due 2096	Dec. 31, 2012 7.500% Debentures due 2096	Dec. 31, 2013 7.250% Debentures due 2096	Dec. 31, 2012 7.250% Debentures due 2096
Debt Instrument [Line Items]
Principal	$ 15,202		$ 14,952			$ 275	$ 275	$ 500	$ 500	$ 1,750	$ 1,750	$ 2,000	$ 2,000	$ 114	$ 114	$ 250	$ 0	$ 300	$ 300	$ 600	$ 600	$ 500	$ 500	$ 670	$ 670	$ 650	$ 650	$ 112	$ 112	$ 54	$ 54	$ 150	$ 150	$ 17	$ 17	$ 235	$ 235	$ 135	$ 135	$ 117	$ 117	$ 900	$ 900	$ 500	$ 500	$ 2,360	$ 2,360	$ 1,750	$ 1,750	$ 325	$ 325	$ 750	$ 750	$ 61	$ 61	$ 78	$ 78	$ 49	$ 49
Debt instrument, stated interest rate						5.75%		7.625%		5.95%		6.375%		7.05%		2.60%		6.95%		8.70%		5.375%		4.00%		6.95%		7.50%		7.00%		7.125%		6.625%		7.15%		7.20%		7.95%		7.50%		7.875%				6.45%		7.95%		6.20%		7.73%		7.50%		7.25%
Debt instrument, maturity date						Jun. 15, 2014		Mar. 15, 2014		Sep. 15, 2016		Sep. 15, 2017		May 15, 2018		Aug. 15, 2018		Jun. 15, 2019		Mar. 15, 2019		Jun. 01, 2021		Jun. 01, 2022		Jun. 01, 2024		Oct. 15, 2026		Nov. 15, 2027		Oct. 15, 2027		Jan. 15, 2028		May 15, 2028		Mar. 15, 2029		Apr. 15, 2029		May 01, 2031		Sep. 15, 2031		Oct. 10, 2036		Sep. 15, 2036		Jun. 15, 2039		Mar. 15, 2040		Sep. 15, 2096		Nov. 01, 2096		Nov. 15, 2096
Net unamortized discounts and premiums (1)	(1,645)	[1]	(1,683)	[1]
Total borrowings	13,557		13,269		15,230																																									727
Capital lease obligation	8		0
Current portion of long-term debt	500		0
Total long-term debt	$ 13,065		$ 13,269

[1] Unamortized discounts and premiums are amortized over the term of the related debt.