STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Income	$ 58,241	$ 52,889	$ 43,925
Provided by Operating Activities:
Depreciation and Amortization	44,171	41,959	39,502
Provision for Losses on Accounts Receivable	4,775	1,410	3,741
CIP Receivable	(18,106)	(1,289)	4,381
Deferred Gas Costs - Net of Recoveries	25,050	(37,343)	22,492
Deferred SBC Costs - Net of Recoveries	(4,183)	(4,402)	(2,344)
Environmental Remediation Costs - Net of Recoveries	(188)	(13,612)	(3,530)
Deferred and Noncurrent Income Taxes and Credits - Net	38,353	35,037	24,540
Gas Plant Cost of Removal	(2,133)	(1,590)	(1,596)
Pension Contributions	(19,757)	0	(6,405)
Changes in:
Accounts Receivable	(34,263)	37,428	(13,262)
Inventories	13,449	(6,285)	5,945
Prepaid and Accrued Taxes - Net	6,451	(7,831)	(8,744)
Other Prepayments and Current Assets	430	(1,420)	(105)
Gas Purchases Payable	(2,941)	(9,048)	7,285
Accounts Payable and Other Accrued Liabilities	(8,803)	21,079	(4,017)
Other Assets	(10,980)	(6,294)	(5,886)
Other Liabilities	3,807	9,789	6,657
Net Cash Provided by Operating Activities	93,373	110,477	112,579
Cash Flows from Investing Activities:
Capital Expenditures	(156,041)	(142,570)	(115,466)
Net Proceeds from (Purchase of) Restricted Investments in Margin Account	930	2,103	(4,169)
Investment in Long-Term Receivables	(6,243)	(4,926)	(3,313)
Proceeds from Long-Term Receivables	8,182	6,312	2,901
Net Cash Used in Investing Activities	(153,172)	(139,081)	(120,047)
Cash Flows from Financing Activities:
Net Borrowings from (Repayments of) Lines of Credit	(24,500)	67,700	(50,500)
Proceeds from Issuance of Long-Term Debt	120,000	0	115,000
Principal Repayments of Long-Term Debt	(35,000)	(25,000)	(10,000)
Premium for Early Retirement of Debt	(700)
Payments for Issuance of Long-Term Debt	(951)	(43)	(1,215)
Dividends on Common Stock	0	(12,664)	(45,905)
Excess Tax Benefit from Restricted Stock Plan	124	85	125
Net Cash Provided by Financing Activities	58,973	30,078	7,505
Net (Decrease) Increase in Cash and Cash Equivalents	(826)	1,474	37
Cash and Cash Equivalents at Beginning of Period	3,504	2,030	1,993
Cash and Cash Equivalents at End of Period	2,678	3,504	2,030
Supplemental Disclosures of Cash Flow Information
Interest (Net of Amounts Capitalized)	12,073	20,068	17,611
Income Taxes (Net of Refunds)	(2,797)	(1,044)	14,816
Supplemental Disclosures of Noncash Investing Activities
Property and equipment acquired on account but not paid at year-end	$ 11,069	$ 12,171	$ 14,906