BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, plant and equipment
Property, plant and equipment	$ 6,433,119	$ 6,073,143
Accumulated depreciation and amortization	1,867,893	1,789,431
Net property, plant and equipment	4,565,226	4,283,712
Current assets
Cash and cash equivalents	17,853	21,323
Accounts receivable, net	260,012	295,421
Materials and supplies	55,732	44,333
Natural gas in storage	104,259	107,295
Regulatory assets	47,440	54,420
Other current assets	20,906	20,495
Total current assets	506,202	543,287
Goodwill and other assets
Regulatory assets	391,036	437,479
Goodwill	157,953	157,953
Other assets	87,883	46,211
Total goodwill and other assets	636,872	641,643
Total assets	5,708,300	5,468,642
Equity and long-term debt
Common stock, $0.01 par value: authorized 250,000,000 shares; issued and outstanding 52,771,749 shares at December 31, 2019; issued 52,598,005 shares and outstanding 52,564,902 shares at December 31, 2018	528	526
Paid-in capital	1,733,092	1,727,492
Retained earnings	402,509	320,869
Accumulated other comprehensive income (loss)	(6,739)	(4,086)
Treasury stock, at cost: 33,103 shares at December 31, 2018	0	(2,145)
Total equity	2,129,390	2,042,656
Long-term debt, excluding current maturities, and net of issuance costs of $10,936 and $11,457, respectively	1,286,064	1,285,483
Total equity and long-term debt	3,415,454	3,328,139
Current liabilities
Notes payable	516,500	299,500
Accounts payable	120,490	174,510
Accrued taxes other than income	47,956	47,640
Customer deposits	57,987	61,183
Regulatory liabilities	45,201	48,394
Other current liabilities	84,603	67,664
Total current liabilities	872,737	698,891
Deferred credits and other liabilities [Abstract]
Deferred income taxes	682,632	652,426
Regulatory Liability, Noncurrent	503,518	520,866
Employee benefit obligations	115,657	178,720
Other deferred credits	118,302	89,600
Total deferred credits and other liabilities	1,420,109	1,441,612
Commitments and Contingencies
Total liabilities and equity	$ 5,708,300	$ 5,468,642