Income Taxes (Income Tax Expense Reconciled to Federal Income Tax Rate) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 741	$ 768	$ 704
Income tax expense at 35% statutory rate	260	269	246
Production tax credits	(15)	(5)	0
Investment tax credits	(5)	(6)	(6)
Depreciation	3	3	3
AFUDC - Equity	(5)	(4)	(1)
Employee Stock Ownership Plan dividends	(2)	(3)	(3)
Domestic production activities deduction	(18)	(16)	(6)
State and other income taxes, net of federal benefit	41	40	39
Other, net	(5)	4	(5)
Income Tax Expense (Benefit)	$ 254	$ 282	$ 267
Effective Income Tax Rate	34.30%	36.70%	38.00%