Consolidated Balance Sheets (Unaudited) - USD ($)	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Current assets:
Cash and cash equivalents	$ 15,780,000	$ 3,521,000	$ 6,230,000
Accounts receivable	23,450,000	66,700,000	25,506,000
Accrued unbilled revenue	15,974,000	64,946,000	15,537,000
Allowance for uncollectible accounts	(459,000)	(1,290,000)	(289,000)
Regulatory assets	49,504,000	42,362,000	55,280,000
Derivative instruments	2,073,000	17,031,000	4,857,000
Inventories	59,549,000	54,129,000	67,470,000
Gas reserves	16,218,000	15,926,000	16,257,000
Income taxes receivable	0	0	2,257,000
Other current assets	17,457,000	24,728,000	17,480,000
Total current assets	199,546,000	288,053,000	210,585,000
Non-current assets:
Property, plant, and equipment	3,384,122,000	3,208,816,000	3,177,196,000
Less: Accumulated depreciation	986,332,000	947,916,000	943,334,000
Total property, plant, and equipment, net	2,397,790,000	2,260,900,000	2,233,862,000
Gas reserves	87,876,000	100,184,000	103,976,000
Regulatory assets	345,352,000	357,530,000	341,188,000
Derivative instruments	1,555,000	3,265,000	1,151,000
Other investments	69,245,000	68,376,000	67,853,000
Other non-current assets	4,243,000	1,493,000	1,269,000
Total non-current assets	2,906,061,000	2,791,748,000	2,749,299,000
Total assets	3,105,607,000	3,079,801,000	2,959,884,000
Current liabilities:
Short-term debt	0	53,300,000	194,900,000
Current maturities of long-term debt	21,995,000	39,989,000	64,994,000
Accounts payable	87,475,000	85,664,000	55,933,000
Taxes accrued	12,295,000	12,149,000	11,954,000
Interest accrued	9,854,000	5,966,000	9,671,000
Regulatory liabilities	34,659,000	40,290,000	27,921,000
Derivative instruments	8,968,000	1,315,000	5,334,000
Other current liabilities	27,705,000	35,844,000	31,997,000
Total current liabilities	202,951,000	274,517,000	402,704,000
Long-term debt	757,429,000	679,334,000	530,219,000
Deferred credits and other non-current liabilities:
Deferred tax liabilities	572,293,000	557,085,000	544,575,000
Regulatory liabilities	363,838,000	349,319,000	342,143,000
Pension and other postretirement benefit liabilities	212,259,000	225,725,000	216,909,000
Derivative instruments	3,926,000	913,000	1,682,000
Other non-current liabilities	146,229,000	142,411,000	142,450,000
Total deferred credits and other non-current liabilities	1,298,545,000	1,275,453,000	1,247,759,000
Commitments and contingencies (see Note 13 and Note 14)
Equity:
Common stock - no par value; authorized 100,000 shares; issued and outstanding 28,713, 27,558, and 28,630 at September 30, 2017 and 2016, and December 31, 2016, respectively	447,129,000	445,187,000	389,834,000
Retained earnings	406,081,000	412,261,000	396,938,000
Accumulated other comprehensive loss	(6,528,000)	(6,951,000)	(7,570,000)
Total equity	846,682,000	850,497,000	779,202,000
Total liabilities and equity	$ 3,105,607,000	$ 3,079,801,000	$ 2,959,884,000