Employee Benefit Plans (Amounts Included in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost in Subsequent Year) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost	$ (12)
Amortization of actuarial (gain) loss, net	93
Total accumulated other comprehensive income expected to be recognized as components of net periodic (benefit) cost in the next year	81
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost	(12)
Amortization of actuarial (gain) loss, net	58
Total accumulated other comprehensive income expected to be recognized as components of net periodic (benefit) cost in the next year	$ 46