Supplemental Information on Oil and Gas Producing Activities (Unaudited) (Detail 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 MMcfe	Dec. 31, 2013 MMcfe	Dec. 31, 2012 MMcfe	Dec. 31, 2011
oil and gas reserves
Extensions, discoveries and other additions	6,444,000	3,682,000	1,951,000
Increase decrease in proved reserve due to relcassifications	(1,417,000)
Reduction of proved reserves resulted from downward price revisions		788,000	102,000
Sales of proved reserves			(2,174,000)
Increase (decrease) in proved reserves due to performance revisions	361,000.000		324,000.000
Initial period to drill well		5 years
Annual net cash inflows
Period of unweighted first day of the month average prices used to compute future cash inflows		12 months
Future cash inflows	$ 63,632	$ 30,113	$ 12,151
Future production costs	21,722	5,967	1,660
Future development costs	8,212	5,349	3,270
Future net cash flows before income tax	33,698	18,797	7,221
Future income tax expense	10,726	5,308	1,603
Future net cash flows	22,972	13,489	5,618
10% annual discount for estimated timing of cash flows	(15,337)	(8,979)	(4,017)
Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Total	$ 7,635	$ 4,510	$ 1,601	$ 2,470
NGLs and oil
oil and gas reserves
Extensions, discoveries and other additions			709,000
Increase (decrease) in proved reserves due to performance revisions	2.000
Initial period to drill well	5 years	5 years
Number of horizontal producing wells acquired	5
Number of dry gas locations	191
Future cash inflows computation period	12 months
Percentage of net cash inflows that were dicounted at annual rate	10.00%
Arkoma and Piceance Basin
oil and gas reserves
Sales of proved reserves			2,174,000