Employee Benefit Plans (Schedule of Changes, Net of Tax, in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net loss arising during the period	$ (192)	$ (176)	$ (100)
Amortization of net actuarial loss	(62)	(42)	(30)
Amortization of prior service cost (credit)	3	3	5
Amortization of transition obligation	4	4	4
Total recognized in other comprehensive income (loss)	(123)	(127)	(61)
Defined Benefit Pension Plans | Qualified Plan
Net loss arising during the period	(160)
Amortization of net actuarial loss	(54)
Amortization of prior service cost (credit)	4
Amortization of transition obligation	0
Total recognized in other comprehensive income (loss)	(102)
Defined Benefit Pension Plans | Non-Qualified Plan
Net loss arising during the period	(30)
Amortization of net actuarial loss	(7)
Amortization of prior service cost (credit)	(2)
Amortization of transition obligation	0
Total recognized in other comprehensive income (loss)	(25)
Postretirement Benefit Plan
Net loss arising during the period	(2)
Amortization of net actuarial loss	(1)
Amortization of prior service cost (credit)	1
Amortization of transition obligation	4
Total recognized in other comprehensive income (loss)	$ 4