CONSOLIDATED STATEMENTS OF CAPITALIZATION - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Schedule of Capitalization, Long-term Debt [Line Items]
Unamortized discount		$ (2,865)	$ (3,131)
Unamortized Debt Issuance Expense		(4,697)	(5,144)
Total long-term debt, including current maturities		663,069	662,449
Less: current maturities		1,123	1,131
Total long-term debt		661,946	661,318
Common Stockholders' Equity
Common stock — 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at Dec. 31, 2016 and 2015, respectively		93,300	93,300
Additional paid in capital		395,315	394,553
Retained earnings		323,368	302,741
Accumulated other comprehensive loss		(133)	(209)
Total common stockholder’s equity		811,850	790,385
First Mortgage Bonds | Series Due Oct. 1, 2018
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross		150,000	150,000
First Mortgage Bonds | Series Due June 15, 2024
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross		200,000	200,000
First Mortgage Bonds | Series Due Sept. 1, 2038
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross		200,000	200,000
First Mortgage Bonds | Series Due Oct. 1, 2042
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross		100,000	100,000
City of La Crosse Resource Recovery Bond | Series Due Nov. 1, 2021
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross	[1]	18,600	18,600
Fort McCoy System Acquisition | Due Oct. 15, 2030
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross		456	490
Other
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross		$ 1,575	$ 1,634

[1] Resource recovery financing