Pension Plans, Retirement Benefits and Savings Plans (details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Plans [Member]
Defined benefit plan disclosure
Service cost	$ 29	$ 28
Interest cost on benefit obligation	33	35
Expected return on plan assets	(52)	(47)
Amortization of unrecognized net actuarial loss	27	22
Net periodic benefit cost, net benefit expense	37	38
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Interest cost on benefit obligation	2	3
Net periodic benefit cost, net benefit expense	$ 2	$ 3