Pension Benefits (Companies' Net Periodic Benefit Costs) (Details) (Pension Benefits [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - including administrative expenses	$ 59	$ 47
Interest cost on projected benefit obligation	137	140
Expected return on plan assets	(176)	(183)
Amortization of net actuarial loss	177	132
Amortization of prior service costs	2	2
NET PERIODIC BENEFIT COST	199	138
Cost capitalized	(64)	(48)
Cost deferred	(37)	(51)
Cost charged to operating expenses	98	39
Estimated future employer contributions	775
Expect to fund	$ 12