Merger Assets and Liabilities Acquired (Details) (Berkshire Hathaway, Inc. [Member], USD $) In Millions, unless otherwise specified	Feb. 12, 2010
Berkshire Hathaway, Inc. [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	$ 971
Accounts receivable	808
Materials and supplies	630
Current portion of deferred income taxes	210
Other current assets	144
Property and equipment	43,987
Goodwill	14,803
Intangible assets	2,025
Other assets	2,095
Total assets	65,673
Accounts Payable and Other Current Liabilities	2,261
Long-term debt due within one year	649
Long-term debt	10,493
Deferred income taxes	13,413
Intangible liabilities	2,056
Casualty and environmental liabilities	928
Pension and retiree health and welfare liability	865
Other liabilities	513
Net assets acquired	34,495
Total liabilities and net assets acquired	$ 65,673