Income Taxes (Net Deferred Income Tax Liability Components) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Income Taxes [Abstract]
Deferred credits and other liabilities	$ 790		$ 679
Tax credit carryforwards	930	[1]	554
Other	137		100
Total deferred income tax assets	1,857		1,333
Valuation allowance	(144)		(145)
Net deferred income tax assets	1,713		1,188
Investments and other assets	(809)		(781)
Accelerated depreciation rates	(6,989)		(6,052)
Regulatory assets and deferred debits	(1,219)		(996)
Total deferred income tax liabilities	(9,017)		(7,829)
Total net deferred income tax liabilities	$ (7,304)		$ (6,641)

[1] See Tax Credits and NOL Carryforwards table below.