Accumulated Other Comprehensive Income (Loss) (Reclassification out of AOCI) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax benefit resulting from OCI allocation	$ 538	$ 569	$ 0
Non-cash tax provision	538	569	0
Amounts reclassified from accumulated other comprehensive income (loss)	(108)	127
Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	34	(3)
Prior Service Cost [Member] | Pension And Retiree Medical Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	(223)	(72)
Actuarial Loss [Member] | Pension And Retiree Medical Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	81	202
AA [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax benefit resulting from OCI allocation	538	569	0
Non-cash tax provision	538	569	0
Amounts reclassified from accumulated other comprehensive income (loss)	(108)	127
AA [Member] | Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	34	(3)
AA [Member] | Prior Service Cost [Member] | Pension And Retiree Medical Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	(223)	(72)
AA [Member] | Actuarial Loss [Member] | Pension And Retiree Medical Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	$ 81	$ 202