CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Current assets
Cash and cash equivalents	$ 1,285		$ 1,349
Accounts receivable, net	60,396	[1]	59,269	[1]
Accrued unbilled revenues	53,567		51,634
Inventories	24,685		21,475
Regulatory assets	20,036		14,866
Prepaid taxes	28,628		27,518
Deferred income taxes	8,201		14,953
Prepayments and other	6,918		5,056
Total current assets	203,716		196,120
Property, plant and equipment, net	1,674,281		1,442,779
Other assets
Regulatory assets	280,693		233,193
Other investments	3,818		3,650
Other	4,612		3,651
Total other assets	289,123		240,494
Total assets	2,167,120		1,879,393
Current liabilities
Current portion of long-term debt	1,235		107
Short-term debt	78,000		68,000
Notes payable to affiliates	500		470
Accounts payable	61,530		52,086
Accounts payable to affiliates	26,524		24,986
Dividends payable to parent	14,957		8,032
Regulatory liabilities	16,940		9,717
Environmental liabilities	29,116		28,785
Other	19,923		22,521
Total current liabilities	248,725		214,704
Deferred credits and other liabilities
Deferred income taxes	348,180		305,139
Deferred investment tax credits	9,089		9,698
Regulatory liabilities	132,674		126,424
Environmental liabilities	78,620		79,703
Customer advances	17,623		16,008
Pension and employee benefit obligations	51,313		45,708
Other	16,151		9,237
Total deferred credits and other liabilities	653,650		591,917
Commitments and contingencies
Capitalization
Long-term debt	567,056		468,490
Common stock — 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at Dec. 31, 2014 and 2013, respectively	93,300		93,300
Additional paid in capital	322,276		248,844
Retained earnings	282,398		262,499
Accumulated other comprehensive loss	(285)		(361)
Total common stockholder’s equity	697,689		604,282
Total liabilities and equity	$ 2,167,120		$ 1,879,393

[1] Accounts receivable, net includes an immaterial amount and $1,595 due from affiliates for 2014 and 2013, respectively.