Benefit Obligations (Plan Assets Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Asset/liability study	A formal asset/liability study of each plan is undertaken every 3 to 5 years or whenever there has been a material change in plan demographics, benefit structure or funding status and investment market.
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated employer contributions for pension benefits and postretirement benefits	137
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated employer contributions for pension benefits and postretirement benefits	25
Nonqualified Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated employer contributions for pension benefits and postretirement benefits	20