Employee Benefit Plans (Quarterly Info) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension Benefits [Member]
Components of net periodic benefit cost:
Service cost	$ 10	$ 11	$ 30	$ 33
Interest cost	15	12	46	38
Expected return on plan assets	(19)	(15)	(57)	(45)
Amortization of prior service cost (credit)	0	1	0	1
Amortization of net actuarial loss	10	15	29	45
Net periodic benefit cost (credit)	16	24	48	72
Employer contributions			61
Estimated future employer contributions in current fiscal year			2
Other Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	0	1	1	2
Interest cost	2	2	7	8
Expected return on plan assets	(3)	(3)	(9)	(7)
Amortization of prior service cost (credit)	(5)	(3)	(15)	(7)
Amortization of net actuarial loss	0	1	0	4
Reclassification to regulatory liability	1	1	3	1
Net periodic benefit cost (credit)	(5)	(1)	(13)	1
Amortization of prior service cost (credit) from regulatory assets (liabilities)	(3)	(1)	(9)	(4)
Amortization of net actuarial loss (gain) from regulatory assets (liabilities)	0	0	0	2
Employer contributions			5
Estimated future employer contributions in current fiscal year			$ 1