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Supplemental Financial Statement Information (Valuation Accounts) (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Supplemental Financial Statement Information
Accumulated depreciation	$ 19,492	$ 18,991
Allowance for doubtful accounts	$ 140	$ 129

- Definition

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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