CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
OPERATING ACTIVITIES:
Net Income	$ 67,890	$ 39,709
Items not affecting cash:
Depreciation	84,685	79,364
Amortization of debt issue costs, discount and deferred hedge gain	290	273
Amortization of restricted stock	1,826	2,199
Equity portion of allowance for funds used during construction	(3,572)	(3,311)
Gain on disposition of assets	(761)	(232)
Deferred income taxes	41,159	21,663
Mountain States Transmission Intertie impairment	0	24,039
Changes in current assets and liabilities:
Restricted cash	(1,536)	4,731
Accounts receivable	14,500	37,688
Inventories	(8,462)	156
Other current assets	(1,983)	(712)
Accounts payable	(19,512)	(9,604)
Accrued expenses	22,358	29,139
Regulatory assets	9,384	(3,266)
Regulatory liabilities	(8,209)	10,573
Other noncurrent assets	(32,298)	(13,400)
Other noncurrent liabilities	5,579	3,619
Cash provided by operating activities	171,338	222,628
INVESTING ACTIVITIES:
Property, plant, and equipment additions	(153,951)	(157,859)
Asset acquisition	0	(18,384)
Proceeds from sale of assets	3,887	262
Cash used in investing activities	(150,064)	(175,981)
FINANCING ACTIVITIES:
Treasury stock activity	(1,107)	(557)
Proceeds from issuance of common stock, net	44,102	28,477
Dividends on common stock	(43,103)	(40,584)
Issuance of long-term debt	0	150,000
Repayments on long-term debt	(113)	(3,871)
Repayments of short-term borrowings, net	(19,954)	(166,934)
Financing costs	0	(910)
Cash used in financing activities	(20,175)	(34,379)
Increase in Cash and Cash Equivalents	1,099	12,268
Cash and Cash Equivalents, beginning of period	9,822	5,928
Cash and Cash Equivalents, end of period	10,921	18,196
Cash paid during the period for:
Income taxes	47	1,944
Interest	40,873	34,416
Significant non-cash transactions:
Capital expenditures included in accounts payable and accrued expenses	$ 11,245	$ 13,292