Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Current assets:
Cash and cash equivalents	$ 29,965	$ 3,472	$ 15,780
Accounts receivable	25,125	66,236	21,930
Accrued unbilled revenue	16,351	62,381	15,974
Allowance for uncollectible accounts	(394)	(956)	(459)
Regulatory assets	41,241	45,781	49,504
Derivative instruments	2,871	1,735	2,073
Inventories	53,064	47,577	59,135
Gas reserves	16,916	15,704	16,218
Other current assets	20,376	24,949	17,285
Discontinued operations current assets	12,644	3,057	2,106
Total current assets	218,159	269,936	199,546
Non-current assets:
Property, plant, and equipment	3,370,388	3,204,635	3,148,545
Less: Accumulated depreciation	996,994	960,477	954,782
Total property, plant, and equipment, net	2,373,394	2,244,158	2,193,763
Gas reserves	70,556	84,053	87,876
Regulatory assets	333,917	356,608	345,352
Derivative instruments	861	1,306	1,555
Other investments	65,113	66,363	69,245
Goodwill	6,563	0	0
Other non-current assets	12,844	6,505	4,192
Discontinued operations - non-current assets	0	10,817	204,078
Total non-current assets	2,863,248	2,769,810	2,906,061
Total assets	3,081,407	3,039,746	3,105,607
Current liabilities:
Short-term debt	100,500	54,200	0
Current maturities of long-term debt	84,940	96,703	21,995
Accounts payable	80,143	111,021	87,123
Taxes accrued	13,074	18,883	11,933
Interest accrued	9,453	6,773	9,854
Regulatory liabilities	37,504	34,013	34,659
Derivative instruments	8,828	18,722	8,968
Other current liabilities	35,497	39,942	27,218
Discontinued operations - current liabilities	13,003	1,593	1,201
Total current liabilities	382,942	381,850	202,951
Long-term debt	724,654	683,184	757,429
Deferred credits and other non-current liabilities:
Deferred tax liabilities	274,315	270,526	572,293
Regulatory liabilities	606,175	586,093	363,838
Pension and other postretirement benefit liabilities	212,249	223,333	212,259
Derivative instruments	3,016	4,649	3,926
Other non-current liabilities	140,475	135,292	134,123
Discontinued operations - non-current liabilities	0	12,043	12,106
Total deferred credits and other non-current liabilities	1,236,230	1,231,936	1,298,545
Commitments and contingencies (Note 15)
Equity:
Common stock - no par value; authorized 100,000 shares; issued and outstanding 28,844, 28,713, and 28,736 at September 30, 2018 and 2017, and December 31, 2017, respectively	455,499	448,865	447,129
Retained earnings	290,059	302,349	406,081
Accumulated other comprehensive loss	(7,977)	(8,438)	(6,528)
Total equity	737,581	742,776	846,682
Total liabilities and equity	$ 3,081,407	$ 3,039,746	$ 3,105,607