Benefit Obligations (Schedule of Company Commitments to Fund Benefit Obligations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Cash Contributions to Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Commitments to fund benefit obligations	$ 9
Commitments to fund benefit obligations, expected	30
Benefit Payments to Nonqualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Commitments to fund benefit obligations	6
Commitments to fund benefit obligations, expected	22
Benefit Payments to Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Commitments to fund benefit obligations	4
Commitments to fund benefit obligations, expected	$ 24