CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Utility Plant
Plant in Service	$ 5,780,805	$ 5,975,139
Utility Plant Under Capital Leases	84,870	167,413
Construction Work in Progress	160,288	129,955
Total Utility Plant	6,025,963	6,272,507
Accumulated Depreciation and Amortization	(2,193,656)	(2,385,053)
Accumulated Amortization of Capital Lease Assets	(63,605)	(104,648)
Total Utility Plant, Net	3,768,702	3,782,806
Investments and Other Property	51,260	45,020
Current Assets
Cash and Cash Equivalents	37,701	35,962
Accounts Receivable, Net	137,932	124,934
Fuel Inventory	25,059	25,887
Materials and Supplies	103,981	97,126
Regulatory Assets	93,960	56,340
Derivative Instruments	3,187	4,966
Other	10,777	13,793
Total Current Assets	412,597	359,008
Regulatory and Other Assets
Regulatory Assets	293,551	225,453
Derivative Instruments	8,826	330
Other	55,313	37,372
Total Regulatory and Other Assets	357,690	263,155
Total Assets	4,590,249	4,449,989
Capitalization
Common Stock (No Par Value, 75,000,000 Shares Authorized, 32,139,434 Shares Outstanding as of December 31, 2017 and 2016)	1,296,539	1,296,539
Capital Stock Expense	(6,357)	(6,357)
Retained Earnings	380,076	273,408
Accumulated Other Comprehensive Loss	(6,226)	(4,555)
Total Common Stock Equity	1,664,032	1,559,035
Preferred Stock (No Par Value, 1,000,000 Shares Authorized, None Outstanding as of December 31, 2017 and 2016)	0	0
Capital Lease Obligations	28,519	39,267
Long-term Debt	1,354,423	1,453,072
Total Capitalization	3,046,974	3,051,374
Current Liabilities
Current Maturities of Long-Term Debt	100,000	0
Borrowings Under Revolving Credit Facility	35,000	0
Capital Lease Obligations	10,749	51,765
Accounts Payable	97,367	89,797
Accrued Taxes Other than Income Taxes	40,706	37,639
Accrued Employee Expenses	30,929	29,465
Accrued Interest	14,750	14,508
Regulatory Liabilities	89,024	76,069
Customer Deposits	24,865	25,778
Derivative Instruments	10,667	2,641
Other	18,119	17,837
Total Current Liabilities	472,176	345,499
Regulatory and Other Liabilities
Deferred Income Taxes, Net	300,258	529,148
Regulatory Liabilities	516,438	300,700
Pension and Other Postretirement Benefits	133,799	131,630
Derivative Instruments	17,907	2,629
Other	102,697	89,009
Total Regulatory and Other Liabilities	1,071,099	1,053,116
Commitments and Contingencies
Total Capitalization and Other Liabilities	$ 4,590,249	$ 4,449,989