Employee Benefits (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Pension Benefits [Member]
Net actuarial loss and prior service cost included in accumulated other comprehensive income [Abstract]
Net actuarial loss	$ 928	$ 637
Prior service cost	20	24
Total net actuarial loss and prior service cost included in accumulated other comprehensive income	948	661
Other Postretirement Benefits [Member]
Net actuarial loss and prior service cost included in accumulated other comprehensive income [Abstract]
Net actuarial loss	122	80
Prior service cost	0	0
Total net actuarial loss and prior service cost included in accumulated other comprehensive income	$ 122	$ 80