CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents		$ 1,403	$ 1,546
Accounts receivable, net	[1]	63,200	54,031
Accrued unbilled revenues		60,008	53,638
Other receivables		15,144	657
Inventories		17,758	18,309
Regulatory assets		23,113	18,162
Prepaid taxes		23,606	25,915
Prepayments		3,450	3,128
Total current assets		207,682	175,386
Property, plant and equipment, net		2,088,728	1,947,637
Other assets
Regulatory assets		282,217	286,188
Other investments		2,892	2,844
Other		201	785
Total other assets		285,310	289,817
Total assets		2,581,720	2,412,840
Current liabilities
Current portion of long-term debt		151,080	1,123
Short-term debt		11,000	60,000
Notes payable to affiliates		500	500
Accounts payable		58,365	41,068
Accounts payable to affiliates		29,628	29,037
Dividends payable to parent		15,481	10,729
Regulatory liabilities		20,712	17,428
Environmental liabilities		10,469	41,438
Accrued interest		8,025	8,012
Other		34,474	26,484
Total current liabilities		339,734	235,819
Deferred credits and other liabilities
Deferred income taxes		256,687	430,593
Deferred investment tax credits		7,514	8,037
Regulatory liabilities		386,807	148,189
Environmental liabilities		19,190	23,003
Customer advances		16,325	19,425
Pension and employee benefit obligations		50,027	55,164
Other		18,747	18,814
Total deferred credits and other liabilities		755,297	703,225
Commitments and contingencies
Capitalization
Long-term debt		610,100	661,946
Common stock — 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at Dec. 31, 2017 and 2016, respectively		93,300	93,300
Additional paid in capital		449,350	395,315
Retained earnings		334,008	323,368
Accumulated other comprehensive loss		(69)	(133)
Total common stockholder’s equity		876,589	811,850
Total liabilities and equity		$ 2,581,720	$ 2,412,840

[1] Accounts receivable, net includes $3.4 million and an immaterial amount due from affiliates for 2017 and 2016, respectively.