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Depreciation And Amortization	3 Months Ended
Depreciation And Amortization	Mar. 31, 2012
Depreciation And Amortization [Abstract]
Depreciation And Amortization	4. Depreciation and Amortization Accumulated depreciation of owned equipment and property at March 31, 2012 and December 31, 2011 was $10.3 billion and $10.1 billion, respectively. Accumulated amortization of equipment and property under capital leases at March 31, 2012 and December 31, 2011 was $199 million and $448 million, respectively.