Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATIONS:
Net income	$ 58,585	$ 55,861
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	137,271	134,228
Amortization of regulatory assets	2,877	1,435
Deferred income taxes and investment tax credit adjustments - net	(6,412)	(13,427)
Allowance for equity funds used during construction	(2,904)	(503)
Gain on sale of nonutility property	(297)
Change in certain assets and liabilities:
Accounts receivable	843	(4,368)
Fuel, materials and supplies	(6,182)	(6,203)
Income taxes receivable or payable	6,878	11,759
Financial transmission rights	(5,428)	(1,558)
Accounts payable and accrued expenses	(9,546)	(16,966)
Accrued real estate and personal property taxes	4,917	5,462
Accrued interest	14,441	14,151
Pension and other postretirement benefit expenses	(49,741)	(33,895)
Short-term and long-term regulatory assets and liabilities	24,729	13,333
Other - net	(2,785)	(1,123)
Net cash provided by operating activities	167,246	158,186
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures - utility	(161,684)	(82,387)
Grants under the American Recovery and Reinvestment Act of 2009	923	3,833
Cost of removal, net of salvage	(4,148)	(7,225)
Other	(3,795)	(5,398)
Net cash used in investing activities	(168,704)	(91,177)
CASH FLOWS FROM FINANCING ACTIVITIES:
Short-term debt borrowings	145,500	63,000
Short-term debt repayments	(145,500)	(77,000)
Long-term borrowings, net of discount	169,728
Retirement of long-term debt, including make-whole provision	(110,377)
Dividends on common stock	(43,650)	(44,600)
Equity contribution from AES	49,091
Preferred dividends of subsidiary	(2,410)	(2,410)
Deferred financing costs paid	(1,844)	(166)
Other	(6)	(4)
Net cash used in financing activities	60,532	(61,180)
Net change in cash and cash equivalents	59,074	5,829
Cash and cash equivalents at beginning of period	18,487	27,283
Cash and cash equivalents at end of period	77,561	33,112
Supplemental disclosures of cash flow information:
Interest (net of amount capitalized)	63,673	64,108
Income taxes	34,000	40,000
Non-cash financing and investing activities:
Accruals for capital expenditures	$ 23,770	$ 24,097