BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Property, plant and equipment
Property, plant and equipment	$ 4,970,989	$ 4,850,201
Accumulated depreciation and amortization	1,590,940	1,556,481
Net property, plant and equipment	3,380,049	3,293,720
Current assets
Cash and cash equivalents	135,886	11,943
Accounts receivable, net	142,701	326,749
Materials and supplies	31,682	27,511
Income tax receivable	12,156	43,800
Natural gas in storage	119,891	185,300
Regulatory assets (Note 2)	21,360	50,193
Other current assets	13,843	22,005
Total current assets	477,519	667,501
Goodwill and other assets
Regulatory assets (Note 2)	452,711	478,723
Goodwill	157,953	157,953
Other assets	57,728	51,313
Total goodwill and other assets	668,392	687,989
Total assets	4,525,960	4,649,210
Equity and long-term debt
Common stock, $0.01 par value: authorized 250,000,000 shares; issued and outstanding 52,590,112 shares at March 31, 2015; issued and outstanding 52,083,859 at December 31, 2014	526	521
Paid-in Capital	1,764,170	1,758,796
Retained earnings	80,273	39,894
Accumulated other comprehensive income (loss)	(4,892)	(5,174)
Treasury stock	(21,184)	0
Total equity	1,818,893	1,794,037
Long-term debt, excluding current maturities	1,201,308	1,201,311
Total equity and long-term debt	3,020,201	2,995,348
Current liabilities
Current maturities of long-term debt	7	6
Notes payable	0	42,000
Accounts payable	67,819	159,064
Accrued interest	18,888	18,872
Accrued taxes other than income	34,199	44,742
Accrued liabilities	14,651	26,019
Customer deposits	59,179	60,003
Regulatory liabilities	37,354	32,467
Other current liabilities	14,839	9,260
Total current liabilities	246,936	392,433
Deferred credits and other liabilities [Abstract]
Deferred income taxes	900,630	894,585
Employee benefit obligations	277,878	287,779
Other deferred credits	80,315	79,065
Total deferred credits and other liabilities	$ 1,258,823	$ 1,261,429
Commitments and contingencies (Note 9)
Total liabilities and equity	$ 4,525,960	$ 4,649,210