CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
OPERATING ACTIVITIES:
Net Income	$ 120,686us-gaap_NetIncomeLoss	$ 93,983us-gaap_NetIncomeLoss	$ 98,406us-gaap_NetIncomeLoss
Items not affecting cash:
Depreciation and depletion	123,776	112,831	106,044
Amortization of debt issue costs, discount and deferred hedge gain	5,033	2,039	369
Amortization of nonvested shares	3,262us-gaap_ShareBasedCompensation	2,404us-gaap_ShareBasedCompensation	2,759us-gaap_ShareBasedCompensation
Equity portion of allowance for funds used during construction	(6,554)	(5,050)	(4,846)
Gain on disposition of assets	(1,330)us-gaap_GainLossOnSaleOfOtherAssets	(721)us-gaap_GainLossOnSaleOfOtherAssets	(332)us-gaap_GainLossOnSaleOfOtherAssets
Deferred income taxes	(9,612)us-gaap_DeferredIncomeTaxExpenseBenefit	54,617us-gaap_DeferredIncomeTaxExpenseBenefit	51,890us-gaap_DeferredIncomeTaxExpenseBenefit
Mountain States Transmission Intertie impairment	0us-gaap_NoncashProjectAbandonmentCosts	0us-gaap_NoncashProjectAbandonmentCosts	24,039us-gaap_NoncashProjectAbandonmentCosts
Gain on CELP arbitration decision	0nwe_GainOnCelpArbitrationDecision	0nwe_GainOnCelpArbitrationDecision	(47,894)nwe_GainOnCelpArbitrationDecision
Changes in current assets and liabilities:
Restricted cash	(6,408)	(196)	6,016
Accounts receivable	12,622	(30,792)	3,456
Inventories	747us-gaap_IncreaseDecreaseInInventories	181us-gaap_IncreaseDecreaseInInventories	5,371us-gaap_IncreaseDecreaseInInventories
Other current assets	4,201	(2,940)	(1,856)
Accounts payable	(9,565)	6,235	10,976
Accrued expenses	8,530	1,949	14,149
Regulatory assets	(8,952)	(2,846)	(6,285)
Regulatory liabilities	9,763	(2,019)	15,241
Other noncurrent assets	2,853	(43,714)	(27,362)
Other noncurrent liabilities	987	7,755	1,052
Cash provided by operating activities	250,039	193,716	251,193
INVESTING ACTIVITIES:
Property, plant, and equipment additions	(270,384)	(230,454)	(219,234)
Acquisitions	(903,573)	(68,666)	(103,241)
Proceeds from sale of assets	1,535	3,766	262
Change in restricted cash	(16,358)	0	0
Investment in New Market Tax Credit program	(18,169)	0	0
Cash used in investing activities	(1,206,949)	(295,354)	(322,213)
FINANCING ACTIVITIES:
Dividends on common stock	(65,019)us-gaap_PaymentsOfDividendsCommonStock	(57,684)us-gaap_PaymentsOfDividendsCommonStock	(54,246)us-gaap_PaymentsOfDividendsCommonStock
Proceeds from issuance of common stock, net	399,207	56,825	28,477
Issuance of long-term debt	505,789	100,000	150,000
Repayment of long-term debt	(90)us-gaap_RepaymentsOfLongTermDebt	(149)us-gaap_RepaymentsOfLongTermDebt	(3,945)us-gaap_RepaymentsOfLongTermDebt
Issuances (repayments) of short-term borrowings, net	126,890	18,016	(44,000)
Treasury stock activity	(814)us-gaap_ProceedsFromRepurchaseOfEquity	(1,042)us-gaap_ProceedsFromRepurchaseOfEquity	(429)us-gaap_ProceedsFromRepurchaseOfEquity
Financing costs	(5,248)us-gaap_PaymentsOfFinancingCosts	(7,593)us-gaap_PaymentsOfFinancingCosts	(943)us-gaap_PaymentsOfFinancingCosts
Cash provided by financing activities	960,715	108,373	74,914
Increase in Cash and Cash Equivalents	3,805	6,735	3,894
Cash and Cash Equivalents, beginning of period	16,557	9,822	5,928
Cash and Cash Equivalents, end of period	$ 20,362	$ 16,557	$ 9,822

The component of interest expense representing the noncash expenses charged against earnings in the period to allocate debt discount and premium, the costs to issue debt and obtain financing over the related debt instruments, and the amount of expense charged against earnings by an Entity to record deferred gains and losses on hedge instruments.

No definition available.