Acquisition of Atlas Energy Inc. (Details) (USD $) In Millions, unless otherwise specified	Feb. 17, 2011
Allocation of the Purchase price of Atlas's assets and liabilities
Current assets	$ 155
Investments and long-term receivables	456
Properties	6,051
Goodwill	27
Other assets	5
Total assets acquired	6,694
Current liabilities	(560)
Long-term debt and capital leases	(761)
Deferred income taxes	(1,915)
Other liabilities	(25)
Total liabilities assumed	(3,261)
Net assets acquired	$ 3,433