Operating and Administrative Expenses (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Components of Operating Other Cost and Expense [Line Items]
Minimum rental commitments under noncancellable operating leases	$ 1,427
Amounts payable over the next five years
2014	253
2015	213
2016	185
2017	153
2018	113
Equipment For Sublease [Member]
Components of Operating Other Cost and Expense [Line Items]
Rental expense under operating leases	64	149	158
Other Rental Expense [Member]
Components of Operating Other Cost and Expense [Line Items]
Rental expense under operating leases	$ 364	$ 390	$ 434