Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating revenues [Abstract]
Operating revenues	$ 99,183	$ 138,280	$ 354,712	$ 399,945
Operating expenses: [Abstract]
Cost of Gas	20,871	62,176	129,282	187,881
Operations and maintenance	35,962	35,311	74,901	89,427
Environmental Remediation Expense	1,893	0	6,922	0
General taxes	7,438	7,649	16,122	16,381
Depreciation and amortization	20,413	20,230	40,807	40,341
Operating Costs and Expenses	86,577	125,366	268,034	334,030
Income from operations	12,606	12,914	86,678	65,915
Other income and expense, net	513	1,135	(1,796)	6,184
Interest Income (Expense), Nonoperating, Net	9,718	10,438	19,454	20,919
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	3,401	3,611	65,428	51,180
Income tax expense	(1,382)	(1,414)	(26,768)	(20,497)
Net Income	2,019	2,197	38,660	30,683
Other comprehensive income: [Abstract]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax of $126 and $217 for the three months ended and $253 and $433 for the six months ended June 30, 2016 and 2015, respectively	143	331	337	663
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 2,162	$ 2,528	$ 38,997	$ 31,346
Average common shares outstanding: [Abstract]
Basic	27,510	27,343	27,479	27,322
Diluted	27,632	27,388	27,591	27,378
Earnings per share of common stock: [Abstract]
Basic	$ 0.07	$ 0.08	$ 1.41	$ 1.12
Diluted	0.07	0.08	1.40	1.12
Dividends declared per share of common stock	$ 0.4675	$ 0.4650	$ 0.9350	$ 0.9300