Pension Plans and Other Postretirement Benefits Pension Plans and Other Postretirement Benefits - Additional Information (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Pension Plans, Defined Benefit [Member] | Funded Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Contributions	$ 122
Expected employer contributions during the remainder of the current fiscal year	2
Pension Plans, Defined Benefit [Member] | Unfunded Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Contributions	6
Expected employer contributions during the remainder of the current fiscal year	30
Other Postretirement Benefit Plans, Defined Benefit [Member] | Unfunded Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Contributions	11
Expected employer contributions during the remainder of the current fiscal year	$ 5