Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 24	$ 21
Interest cost	40	42
Expected return on plan assets	(54)	(52)
Prior service cost (benefit)	(1)	(1)
Actuarial loss	22	19
Net periodic benefit cost	31	29
Postretirement Benefit Costs [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	6	6
Interest cost	12	13
Expected return on plan assets	(16)	(14)
Prior service cost (benefit)	(1)	(1)
Actuarial loss	2	3
Net periodic benefit cost	$ 3	$ 7