Benefit Plans (Summary of the components of net periodic benefit cost recognized for pension plans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Service cost	$ 105	$ 83	$ 76
Interest cost	103	93	86
Estimated return on plan assets	(197)	(178)	(144)
Net amortization and other	34	24	58
Net periodic benefit cost	45	22	76
Net actuarial loss (gain)	388	133	(228)
Net amortization	(34)	(24)	(58)
Net amount recognized in comprehensive income	354	109	(286)
Total net periodic pension (income) costs recognized in total comprehensive income	$ 399	$ 131	$ (210)