Income Taxes (Tables)

12 Months Ended

Dec. 31, 2011

Income Taxes [Abstract]

Details of income tax provisions

	2011		2010			2009
	(in millions)
Federal —
Current	$	57	$	42		$	771
Deferred		1,035		898			40
	$	1,092		940			811
State —
Current		8		(54	)		100
Deferred		119		140			(15)
		127		86			85
Total	$	1,219	$	1,026		$	896

Tax effects between the carrying amounts of assets and liabilities

	2011			2010
	(in millions)
Deferred tax liabilities —
Accelerated depreciation	$	7,882		$	6,833
Property basis differences		1,256			1,150
Leveraged lease basis differences		277			263
Employee benefit obligations		499			485
Under recovered fuel clause		82			179
Premium on reacquired debt		111			109
Regulatory assets associated with employee benefit obligations		1,198			814
Regulatory assets associated with asset retirement obligations		546			509
Other		276			215
Total		12,127			10,557
Deferred tax assets —
Federal effect of state deferred taxes		393			386
State effect of federal deferred taxes		1			50
Employee benefit obligations		1,594			1,179
Over recovered fuel clause		33			40
Other property basis differences		134			119
Deferred costs		55			100
Cost of removal		40			52
Tax credit carryforward		129			192
Unbilled revenue		110			126
Other comprehensive losses		81			69
Asset retirement obligations		546			509
Other		357			331
Total		3,473			3,153
Total deferred tax liabilities, net		8,654			7,404
Portion included in prepaid expenses (accrued income taxes), net		125			117
Deferred state tax assets		86			91
Valuation allowance		(56	)		(58)
Accumulated deferred income taxes	$	8,809		$	7,554

Reconciliation of federal statutory income tax rate to effective income tax rate

	2011			2010			2009
Federal statutory rate		35.0	%		35.0	%		35.0%
State income tax, net of federal deduction		2.4			1.8			2.1
Employee stock plans dividend deduction		(1.1	)		(1.2	)		(1.4)
Non-deductible book depreciation		0.7			0.8			0.9
Difference in prior years’ deferred and current tax rate		(0.1	)		(0.1	)		(0.1)
AFUDC-Equity		(1.5	)		(2.2	)		(2.7)
Production activities deduction		—			—			(0.7)
ITC basis difference		(0.2	)		(0.4	)		—
Leveraged lease termination		—			—			(0.9)
MC Asset Recovery		—			—			2.7
Donations		—			—			(0.4)
Other		(0.2	)		(0.2	)		(0.1)
Effective income tax rate		35.0	%		33.5	%		34.4%

Changes in unrecognized tax benefits

		0000000000		0000000000		0000000000
	2011		2010		2009
	(in millions)
Unrecognized tax benefits at beginning of year		$ 296		$199		$146
Tax positions from current periods		46		62		53
Tax positions increase from prior periods		1		62		12
Tax positions decrease from prior periods		(111)		(27)		(10)
Reductions due to settlements		(112)		—		—
Reductions due to expired statute of limitations		—		—		(2)
Balance at end of year		$ 120		$296		$199

Impact on effective tax rate

		0000000000		0000000000		0000000000
	2011		2010		2009
	(in millions)
Tax positions impacting the effective tax rate		$  69		$217		$199
Tax positions not impacting the effective tax rate		51		79		—
Balance of unrecognized tax benefits		$120		$296		$199

Accrued interest for unrecognized tax benefits

		0000000000		0000000000		0000000000
	2011		2010		2009
	(in millions)
Interest accrued at beginning of year		$ 29		$21		$15
Interest reclassified due to settlements		(24)		—		—
Interest accrued during the year		5		8		6
Balance at end of year		$ 10		$29		$21