Income Taxes (Effective Income Tax Rate From Continuing Operations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Income Taxes
Income tax at federal statutory rate	$ 47	$ 5	$ 133	$ 62
State income taxes, net of federal effect	9	(6)	19	4
Depreciation	(1)	2	(2)	4
Cross-border energy lease investments	(5)	(2)	15	(4)
Change in estimates and interest related to uncertain and effectively settled tax positions	5		(11)	10
Tax credits	(1)	(1)	(3)	(3)
PHI dividends invested in ESOP plan	(1)		(2)	(2)
Release of valuation allowance				(8)
Change in state deferred tax balances as a result of corporate restructuring		2		(6)
Asset removal costs	(2)	(1)	(4)	(2)
Adjustment to prior year taxes				(1)
Deferred tax basis adjustments		(4)	1
Other, net	4	(1)	(3)	(2)
Consolidated income tax expense related to continuing operations	$ 55	$ (6)	$ 143	$ 52
Income tax at federal statutory rate	35.00%	35.00%	35.00%	35.00%
State income taxes, net of federal effect	6.70%	(37.30%)	5.00%	2.00%
Depreciation	(0.70%)	9.30%	(0.50%)	2.40%
Cross-border energy lease investments	(3.70%)	(10.00%)	3.90%	(2.30%)
Change in estimates and interest related to uncertain and effectively settled tax positions	3.70%	(0.70%)	(2.90%)	5.50%
Tax credits	(0.70%)	(6.00%)	(0.80%)	(1.60%)
PHI dividends invested in ESOP plan	(0.70%)	(3.30%)	(0.50%)	(0.90%)
Release of valuation allowance				(4.40%)
Change in state deferred tax balances as a result of corporate restructuring		14.00%		(3.60%)
Asset removal costs	(1.50%)	(4.70%)	(1.10%)	(1.00%)
Adjustment to prior year taxes		(3.30%)		(0.40%)
Deferred tax basis adjustments		(28.70%)	0.30%	(0.20%)
Other, net	2.60%	(4.30%)	(0.80%)	(1.10%)
Consolidated income tax expense related to continuing operations	40.70%	(40.00%)	37.60%	29.40%