Information Relating to the Consolidated Statement of Cash Flows (Details 1) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Treasury Stock at Cost	Dec. 31, 2010 Treasury Stock at Cost	Dec. 31, 2009 Treasury Stock at Cost	Dec. 31, 2011 Atlas Energy Inc [Member]
Additional Information Relating to the Consolidated Statement of Cash Flows (Textual) [Abstract]
Acquisition of Atlas Energy purchase price							$ 3,009
Advance to Atlas Energy	403						403
Cash payment of equity awards included in net increase in operating working capital							184
Repayment of Atlas debt							761
Payoff of Atlas revolving credit facility							271
Equity, Class of Treasury Stock [Line Items]
Share repurchase value				4,262	775	6
Information Relating to the Consolidated Statement of Cash Flows (Textual) [Abstract]
Reduction for income tax benefits associated with stock options exercised	121	67	25
Stock repurchased during period, shares	42.3	8.8
Stock repurchased during period, value	4,250	750
Proceeds from issuance of tax exempt bonds	374	1,250	350
Noncash additions to Properties, plant and equipment	945	2,753	985
Payment for accrued liabilities			$ 2,450