Pension Plans, Retirement Benefits and Savings Plans (details) - Changes in Level 3 (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 item	Dec. 31, 2011
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	$ 294	$ 287
Level 3 fair value category purchases	82	159
Gross transfers out of Level 3	(24)	(96)
Level 3 fair value category, ending balance	284	294
Number of private equity funds included in pension plan assets	2
Other investments [Member] | Pension Plans [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	18	18
Actual return on plan assets, relating to assets still held	2	(1)
Level 3 fair value category purchases		2
Level 3 fair value category sales	(12)	(1)
Gross transfers out of Level 3	(2)
Level 3 fair value category, ending balance	$ 6	$ 18