Employee Benefit Plans (Details 7) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
The effect of fair-value measurements using significant unobservable inputs on changes in Level 3 plan assets for the period are outlined below
Beginning Balance	$ 1,083	$ 823
Actual Return on Plan Assets
Assets held at the reporting date	109	107
Assets sold during the period	2	(1)
Purchases, Sales and Settlements	186	154
Transfers in and/or out of Level 3	0	0
Ending Balance	1,380	1,083
Corporate [Member]
The effect of fair-value measurements using significant unobservable inputs on changes in Level 3 plan assets for the period are outlined below
Beginning Balance	27	28
Actual Return on Plan Assets
Assets held at the reporting date	0	0
Assets sold during the period	0	0
Purchases, Sales and Settlements	4	(1)
Transfers in and/or out of Level 3	0	0
Ending Balance	31	27
Mortgage-Backed Securities [Member]
The effect of fair-value measurements using significant unobservable inputs on changes in Level 3 plan assets for the period are outlined below
Beginning Balance	2	2
Actual Return on Plan Assets
Assets held at the reporting date	0	0
Assets sold during the period	0	0
Purchases, Sales and Settlements	0	0
Transfers in and/or out of Level 3	0	0
Ending Balance	2	2
Real Estate [Member]
The effect of fair-value measurements using significant unobservable inputs on changes in Level 3 plan assets for the period are outlined below
Beginning Balance	998	738
Actual Return on Plan Assets
Assets held at the reporting date	108	103
Assets sold during the period	2	1
Purchases, Sales and Settlements	182	156
Transfers in and/or out of Level 3	0	0
Ending Balance	1,290	998
Other [Member]
The effect of fair-value measurements using significant unobservable inputs on changes in Level 3 plan assets for the period are outlined below
Beginning Balance	56	55
Actual Return on Plan Assets
Assets held at the reporting date	1	4
Assets sold during the period	0	(2)
Purchases, Sales and Settlements	0	(1)
Transfers in and/or out of Level 3	0	0
Ending Balance	$ 57	$ 56