Retirement Benefits (Changes In Fair Value Measurements Of Level 3 Investments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Private Equity Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value at January 1	$ 920	[1]	$ 795
Relating to assets still held at the reporting date	20		53
Relating to assets sold during the period	102		48
Purchases, sales, settlements (net)			146
Purchases	96
Sales	224		122
Fair Value at December 31	914	[2]	920	[1]
Insurance Group Annuity Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value at January 1	2		3
Sales			1
Fair Value at December 31	$ 2		$ 2

[1] e)Includes limited partnerships that invest primarily in U.S. (92 percent) and European (8 percent) buyout opportunities of a range of privately held companies. The Master Trust does not have the right to redeem its limited partnership investment at its net asset value. Instead, the Master Trust receives distributions as the underlying assets are liquidated. It is estimated that the underlying assets of these funds will be gradually liquidated over the next 1 to 10 years. Additionally, the Master Trust has future funding commitments of approximately $335 million over the next 10 years.

[2] e)Includes limited partnerships that invest primarily in U.S. (92 percent) and European (8 percent) buyout opportunities of a range of privately held companies. The Master Trust does not have the right to redeem its limited partnership investment at its net asset value. Instead, the Master Trust receives distributions as the underlying assets are liquidated. It is estimated that the underlying assets of these funds will be gradually liquidated over the next 1 to 10 years. Additionally, the Master Trust has future funding commitments of approximately $331 million over the next 10 years.