Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating revenues [Abstract]
Operating revenues	$ 87,727	$ 93,128	$ 442,439	$ 493,073
Operating expenses: [Abstract]
Cost of Gas	28,264	35,856	157,546	223,737
Operations and maintenance	34,870	32,031	109,771	121,458
Environmental Remediation Expense	1,191	0	8,113	0
General taxes	7,211	6,772	23,333	23,153
Depreciation and amortization	20,628	20,342	61,435	60,683
Operating Costs and Expenses	92,164	95,001	360,198	429,031
Income from operations	(4,437)	(1,873)	82,241	64,042
Other income and expense, net	652	746	(1,144)	6,930
Interest Income (Expense), Nonoperating, Net	9,729	10,111	29,183	31,030
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	(13,514)	(11,238)	51,914	39,942
Income tax expense	5,474	4,553	(21,294)	(15,944)
Net Income	(8,040)	(6,685)	30,620	23,998
Other comprehensive income: [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax of $709 for the three and nine months ended September 30, 2016	(1,086)	0	(1,086)	0
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax of $223 and $217 for the three months ended and $477 and $650 for the nine months ended September 30, 2016 and 2015, respectively	341	332	678	995
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ (8,785)	$ (6,353)	$ 30,212	$ 24,993
Average common shares outstanding: [Abstract]
Basic	27,554	27,363	27,504	27,336
Diluted	27,554	27,363	27,629	27,399
Earnings per share of common stock: [Abstract]
Basic	$ (0.29)	$ (0.24)	$ 1.11	$ 0.88
Diluted	(0.29)	(0.24)	1.11	0.88
Dividends declared per share of common stock	$ 0.4700	$ 0.4650	$ 1.4025	$ 1.3950