Employee Benefit Plans (Quarterly Info) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Benefits [Member]
Components of net periodic benefit cost:
Service cost	$ 10	$ 11	$ 20	$ 22
Interest cost	15	13	31	26
Expected return on plan assets	(19)	(15)	(38)	(30)
Amortization of net actuarial loss	10	15	19	30
Net periodic benefit cost (credit)	16	24	32	48
Employer contributions			31
Estimated future employer contributions in current fiscal year			32
Other Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	0	0	1	1
Interest cost	3	3	5	6
Expected return on plan assets	(3)	(2)	(6)	(4)
Amortization of prior service cost (credit)	(5)	(2)	(10)	(4)
Amortization of net actuarial loss	0	1	0	3
Reclassification to regulatory liability	1	0	2	0
Net periodic benefit cost (credit)	(4)	0	(8)	2
Amortization of prior service cost (credit) from regulatory assets (liabilities)	(3)	(2)	(6)	(3)
Amortization of net actuarial loss (gain) from regulatory assets (liabilities)	0	1	0	2
Employer contributions			3
Estimated future employer contributions in current fiscal year			$ 4