BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property, plant and equipment
Property, plant and equipment	$ 5,040,313	$ 4,850,201
Accumulated depreciation and amortization	1,604,509	1,556,481
Net property, plant and equipment	3,435,804	3,293,720
Current assets
Cash and cash equivalents	52,974	11,943
Accounts receivable, net	103,406	326,749
Materials and supplies	33,400	27,511
Income tax receivable	23,725	43,800
Natural gas in storage	159,912	185,300
Regulatory assets	31,703	50,193
Other current assets	12,227	22,005
Total current assets	417,347	667,501
Goodwill and other assets
Regulatory assets	440,312	478,723
Goodwill	157,953	157,953
Other assets	54,905	51,313
Total goodwill and other assets	653,170	687,989
Total assets	4,506,321	4,649,210
Equity and long-term debt
Common stock, $0.01 par value: authorized 250,000,000 shares; issued 52,598,005 shares and outstanding 52,151,279 shares at September 30, 2015; issued and outstanding 52,083,859 at December 31, 2014	526	521
Paid-in Capital	1,762,508	1,758,796
Retained earnings	71,746	39,894
Accumulated other comprehensive income (loss)	(4,751)	(5,174)
Treasury stock	(19,108)	0
Total equity	1,810,921	1,794,037
Long-term debt, excluding current maturities	1,201,306	1,201,311
Total equity and long-term debt	3,012,227	2,995,348
Current liabilities
Current maturities of long-term debt	7	6
Notes payable	0	42,000
Accounts payable	57,240	159,064
Accrued interest	7,647	18,872
Accrued taxes other than income	40,429	44,742
Accrued liabilities	18,000	26,019
Customer deposits	58,331	60,003
Regulatory liabilities	41,337	32,467
Other current liabilities	10,478	9,260
Total current liabilities	233,469	392,433
Deferred credits and other liabilities [Abstract]
Deferred income taxes	907,647	894,585
Employee benefit obligations	274,073	287,779
Other deferred credits	78,905	79,065
Total deferred credits and other liabilities	$ 1,260,625	$ 1,261,429
Commitments and contingencies
Total liabilities and equity	$ 4,506,321	$ 4,649,210