2.4.0.82311301 - Disclosure - Gas Reserves (tables)truefalsefalse1false falsefalseD2013Q2YTDhttp://www.sec.gov/CIK0000073020duration2013-01-01T00:00:002013-06-30T00:00:001true 1nwn_GasReservesTableAbstractnwn_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Gas Reserves Table [Abstract]2false 2nwn_GasReservesTableTextBlocknwn_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00<div style="font-family:Times New Roman;font-size:10pt;"><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:100%;border-collapse:collapse;text-align:left;"><tr><td colspan="13" rowspan="1"></td></tr><tr><td width="52%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="13%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="13%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="13%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="font-family:Arial;font-size:9pt;text-align:left;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="7" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:center;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">June 30,</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1"><div style="text-align:center;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">December 31,</font></div></td></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="font-family:Arial;font-size:8pt;font-style:italic;text-align:left;font-size:8pt;"><font style="font-family:Arial;font-size:8pt;font-style:italic;">In thousands</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1"><div style="text-align:center;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">2013</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1"><div style="text-align:center;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">2012</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1"><div style="text-align:center;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">2012</font></div></td></tr><tr><td style="vertical-align:bottom;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:9pt;"><font style="font-family:Arial;font-size:9pt;">Gas reserves, current</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</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:9pt;"><font style="font-family:Arial;font-size:9pt;">$</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">15,324</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">$</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:9pt;"><font style="font-family:Arial;font-size:9pt;">11,021</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><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</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:9pt;"><font style="font-family:Arial;font-size:9pt;">$</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:9pt;"><font style="font-family:Arial;font-size:9pt;">14,966</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:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">Gas reserves, non-current</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">126,215</font></div></td><td style="vertical-align:bottom;" 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><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">69,097</font></div></td><td style="vertical-align:bottom;" 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><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">92,179</font></div></td><td style="vertical-align:bottom;" 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:bottom;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:9pt;"><font style="font-family:Arial;font-size:9pt;">Less: Accumulated amortization</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">12,453</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #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><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">4,071</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #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><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">7,486</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #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><tr><td style="vertical-align:bottom;padding-left:12px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">Total gas reserves</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">129,086</font></div></td><td style="vertical-align:bottom;" 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><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">76,047</font></div></td><td style="vertical-align:bottom;" 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><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">99,659</font></div></td><td style="vertical-align:bottom;" 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:bottom;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:9pt;"><font style="font-family:Arial;font-size:9pt;">Less: Deferred tax liabilities on gas reserves</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">39,963</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #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><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">26,839</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #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><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">28,329</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #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><tr><td style="vertical-align:bottom;padding-left:12px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">Net investment in gas reserves</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;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;" rowspan="1" colspan="1"><div style="text-align:left;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">$</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">89,123</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #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><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;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;" rowspan="1" colspan="1"><div style="text-align:left;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">$</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">49,208</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">&#160;</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">$</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:right;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">71,330</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #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></table></div></div></div>falsefalsefalsenonnum:textBlockItemTypenaTabular disclosure of information pertaining to gas reserves.No definition available.false0Gas Reserves Table [Text Block]falseGas Reserves (tables)UnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.nwnatural.com/role/GasReservesTables12