Income Taxes (Components Of The Net Deferred Tax Liability From Continuing Operations) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Abstract]
Advances and contributions	$ 475,280	$ 463,694
Deferred investment tax credits	11,202	11,789
Other postretirement benefits	101,258	92,620
Tax losses and credits	284,636	327,128
Pension benefits	132,972	141,530
Unamortized debt discount, net	23,872	22,889
Other	13,308	8,429
Deferred tax assets, Gross	1,042,528	1,068,079
Valuation allowance	(20,701)	(22,733)
Deferred tax assets, Net	1,021,827	1,045,346
Utility plant, principally due to depreciation differences	1,958,044	1,846,338
Income taxes recoverable through rates	94,331	93,495
Deferred security costs	1,982	3,065
Deferred business services project expenses	4,573	4,566
Deferred other postretirement benefits	58,238	48,155
Deferred pension benefits	97,899	78,972
Other	95,557	81,005
Deferred Tax Liabilities, Total	2,310,624	2,155,596
Deferred Tax Assets (Liabilities), Net, Total	$ (1,288,797)	$ (1,110,250)