Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating activities:
Net income	$ 54,971	$ 47,396	$ 41,296
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation and amortization including regulatory items	79,751	71,076	62,247
Pension and other postretirement benefit costs, net of contributions	(20,379)	(3,683)	4,096
Deferred income taxes and unamortized investment tax credit, net	45,051	26,880	15,324
Allowance for equity funds used during construction	(294)	(4,538)	(6,209)
Stock compensation expense	2,147	3,478	2,616
Non cash loss on derivatives	1,187	1,853	10,350
Other	381		(457)
Cash flows impacted by changes in:
Accounts receivable and accrued unbilled revenues	10,342	(11,211)	2,989
Fuel, materials and supplies	(16,682)	(1,585)	4,635
Prepaid expenses, other current assets and deferred charges	(23,163)	(19,606)	(7,464)
Accounts payable and accrued liabilities	(318)	(6,179)	(1,305)
Interest, taxes accrued and customer deposits	(980)	1,522	806
Other liabilities and other deferred credits	3,172	3,954	699
SWPA minimum flows payment		26,564
Accumulated provision - rate refunds	(578)
Net cash provided by operating activities	134,608	135,921	129,623
Investing activities:
Capital expenditures - regulated	(99,162)	(106,388)	(154,016)
Capital expenditures and other investments - non-regulated	(3,375)	(2,817)	(1,239)
Proceeds from the sale of property, plant and equipment			544
Restricted cash	(2,586)	(1,771)
Total net cash used in investing activities	(105,123)	(110,976)	(154,711)
Financing activities:
Proceeds from first mortgage bonds, net		149,635	75,000
Proceeds from issuance of notes payable			2,470
Long-term debt issuance costs		(1,758)	(2,397)
Proceeds from issuance of common stock, net of issuance costs	5,884	60,239	70,271
Repayment of first mortgage bonds		(50,000)	(20,025)
Redemption of trust preferred securities		(50,000)
Redemption of senior notes		(48,304)
Net short-term repayments	(12,000)	(26,500)	(51,500)
Dividends	(26,732)	(51,996)	(44,807)
Other	(1,754)	(1,356)	(1,058)
Net cash provided by (used in) financing activities	(34,602)	(20,040)	27,954
Net increase (decrease) in cash and cash equivalents	(5,117)	4,905	2,866
Cash and cash equivalents, beginning of year	10,525	5,620	2,754
Cash and cash equivalents, end of year	5,408	10,525	5,620
Supplemental cash flow information:
Interest paid	41,088	43,044	45,730
Income taxes (refunded) paid, net of refund	(14,300)	11,264	3,246
Supplementary non-cash investing activities:
Change in accrued additions to property, plant and equipment not reported above	(1,387)	(3,846)	(3,833)
Capital lease obligations for purchase of new equipment	$ 29	$ 2,696	$ 2,946