Employee Benefit Plans Employee Benefit Plans - Net Periodic Benefit Cost (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7	$ 10	$ 12
Interest cost	61	63	66
Expected return on plan assets	(74)	(75)	(74)
Net amortization	34	20	13
Net periodic benefit cost	28	18	17
Other Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	7	7	6
Interest cost	28	31	31
Expected return on plan assets	(30)	(30)	(30)
Net amortization	4	18	15
Net periodic benefit cost	$ 9	$ 26	$ 22