Accumulated Other Comprehensive Income (Loss) (Components Of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Beginning balance	$ (4,075)
Current year change	(1,904)
Amortization of actuarial loss and prior service cost	130
Benefit plan modifications	3,345
Reclassification of derivative financial instruments into earnings	(3)
Change in fair value of derivative financial instruments	(12)
Non-cash tax provision	(569)	0	0
Ending balance	(3,088)	(4,075)
Tax benefit resulting from OCI allocation	569	0	0
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred	15
Pension And Retiree Medical Liability [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Beginning balance	(3,887)
Current year change	(1,910)
Amortization of actuarial loss and prior service cost	130
Benefit plan modifications	3,345
Reclassification of derivative financial instruments into earnings	0
Change in fair value of derivative financial instruments	0
Non-cash tax provision	0
Ending balance	(2,322)
Unrealized Gain (Loss) On Investments [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Beginning balance	(4)
Current year change	6
Amortization of actuarial loss and prior service cost	0
Benefit plan modifications
Reclassification of derivative financial instruments into earnings	0
Change in fair value of derivative financial instruments	0
Non-cash tax provision	0
Ending balance	2
Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Beginning balance	28
Current year change
Amortization of actuarial loss and prior service cost	0
Benefit plan modifications
Reclassification of derivative financial instruments into earnings	(3)
Change in fair value of derivative financial instruments	(12)
Non-cash tax provision	0
Ending balance	13
Income Tax Benefit (Expense) [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Beginning balance	(212)
Current year change
Amortization of actuarial loss and prior service cost	0
Benefit plan modifications
Reclassification of derivative financial instruments into earnings	0
Change in fair value of derivative financial instruments	0
Non-cash tax provision	(569)
Ending balance	$ (781)