Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Utility plant:
Land	$ 42,517	$ 40,283
Depreciable plant and equipment	2,729,757	2,522,174
Construction work in progress	175,693	132,957
Intangible assets	22,212	21,925
Total utility plant	2,970,179	2,717,339
Less accumulated depreciation and amortization	(922,214)	(858,062)
Net utility plant	2,047,965	1,859,277
Current assets:
Cash and cash equivalents	94,776	25,492
Receivables: net of allowance for doubtful accounts of $773 and $830 in 2017 and 2016, respectively
Customers	32,451	30,305
Regulatory balancing accounts	36,783	30,332
Other	16,464	17,158
Unbilled revenue	29,756	25,228
Materials and supplies at weighted average cost	6,463	6,292
Taxes, prepaid expenses, and other assets	11,180	7,262
Total current assets	227,873	142,069
Other assets:
Regulatory assets	401,147	355,930
Goodwill	2,615	2,615
Other	60,775	51,854
Total other assets	464,537	410,399
TOTAL ASSETS	2,740,375	2,411,745
Capitalization:
Common stock, $0.01 par value; 68,000 shares authorized, 48,012 and 47,965 outstanding in 2017 and 2016, respectively	480	480
Additional paid-in capital	336,229	334,856
Retained earnings	356,753	324,135
Total common stockholders' equity	693,462	659,471
Long-term debt, less current maturities	515,793	531,745
Total capitalization	1,209,255	1,191,216
Current liabilities:
Current maturities of long-term debt	15,920	26,208
Short-term borrowings	275,100	97,100
Accounts payable	93,955	77,813
Regulatory balancing accounts	59,303	4,759
Accrued other taxes	3,888	3,629
Accrued interest	6,122	5,661
Other accrued liabilities	36,671	35,060
Total current liabilities	490,959	250,230
Unamortized investment tax credits	1,724	1,798
Deferred income taxes	192,946	298,924
Regulatory liabilities	179,706	38,735
Pension and postretirement benefits other than pensions	252,141	222,691
Advances for construction	182,502	182,448
Contributions in aid of construction	186,721	180,790
Other long-term liabilities	44,421	44,913
Commitments and contingencies
TOTAL CAPITALIZATION AND LIABILITIES	$ 2,740,375	$ 2,411,745