2.4.0.82105100 - Disclosure - Goodwilltruefalsefalse1false falsefalseD2013Q2YTDhttp://www.sec.gov/CIK0000073088duration2013-01-01T00:00:002013-06-30T00:00:001true 1nwe_GoodwillAbstractnwe_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Goodwill [Abstract]2false 2us-gaap_GoodwillDisclosureTextBlockus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-weight:bold;">Goodwill</font></div><div style="line-height:120%;text-align:justify;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div><div style="line-height:120%;text-align:left;text-indent:26px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">We completed our annual goodwill impairment test as of April 1, 2013, and no impairments were identified. </font><font style="font-family:inherit;font-size:10pt;">We calculate the fair value of our reporting units by considering various factors, including valuation studies based primarily on a discounted cash flow analysis, with published industry valuations and market data as supporting information. Key assumptions in the determination of fair value include the use of an appropriate discount rate and estimated future cash flows. In estimating cash flows, we incorporate expected long-term growth rates in our service territory, regulatory stability, and commodity prices (where appropriate), as well as other factors that affect our revenue, expense and capital expenditure projections. </font></div><div style="line-height:120%;text-align:left;text-indent:26px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;text-align:left;text-indent:26px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">The</font><font style="font-family:inherit;font-size:10pt;"> long-term growth rates used for our reporting units reflect increased infrastructure investment. However, even if we assumed a 10% reduction in cash flows for either reporting unit, there would be no impairment of goodwill. Additionally, due to our regulated environment, if an increase in the cost of capital occurred, the effect on the corresponding reporting unit's fair value should be ultimately offset by a similar increase in the reporting unit's regulated revenues since those rates include a component that is based on the reporting unit's cost of capital. </font></div><div style="line-height:120%;text-align:left;text-indent:26px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;text-align:left;text-indent:26px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">There were no changes in our goodwill during the </font><font style="font-family:inherit;font-size:10pt;color:#000000;text-decoration:none;">six months ended June 30, 2013</font><font style="font-family:inherit;font-size:10pt;">. Goodwill by segment is as follows for both </font><font style="font-family:inherit;font-size:10pt;color:#000000;text-decoration:none;">June&#160;30, 2013</font><font style="font-family:inherit;font-size:10pt;"> and </font><font style="font-family:inherit;font-size:10pt;color:#000000;text-decoration:none;">December&#160;31, 2012</font><font style="font-family:inherit;font-size:10pt;"> (in thousands):</font></div><div style="line-height:120%;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;font-size:10pt;"><div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:96.6796875%;border-collapse:collapse;text-align:left;"><tr><td colspan="4" rowspan="1"></td></tr><tr><td width="86%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="12%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:top;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Electric</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">$</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:right;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">241,100</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td></tr><tr><td style="vertical-align:top;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Natural gas</font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">114,028</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td></tr><tr><td style="vertical-align:top;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">$</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#cceeff;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:right;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">355,128</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td></tr></table></div><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></div>falsefalsefalsenonnum:textBlockItemTypenaThe entire disclosure for goodwill.No definition available.false0Goodwill Disclosure [Text Block]falseGoodwillUnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.northwesternenergy.com/role/Goodwill12