Depreciation And Amortization (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Depreciation, Depletion and Amortization [Abstract]
Accumulated depreciation of owned equipment and property	$ (10,500,000,000)	$ (10,100,000,000)
Accumulated amortization of equipment and property under capital leases	$ (198,000,000)	$ (448,000,000)