Pensions and Other Postretirement Benefits (Net Periodic Benefit Costs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Defined Contribution Pension [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 15	$ 15
Interest cost	52	56
Expected return on plan assets	(64)	(67)
Amortization of prior service cost	0	0
Amortization of actuarial losses	28	32
Settlement losses (Canada)	18	0
Net periodic pension/other postretirement benefit cost	49	36
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	5
Interest cost	12	14
Expected return on plan assets	0	0
Amortization of prior service cost	(2)	(1)
Amortization of actuarial losses	7	9
Settlement losses (Canada)	0	0
Net periodic pension/other postretirement benefit cost	$ 22	$ 27