2.2.0.7 false Pension and Other Postretirement Benefits 01500 - Disclosure - Pension and Other Postretirement Benefits true false false false 1 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 EPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ 2 Disclosure - Pension and Other Postretirement Benefits 0 nwn_DisclosurePensionAndOtherPostretirementBenefits nwn false na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 3 Pension and Other Postretirement Benefits 1 us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock us-gaap true na duration No definition available. false false false false false false false false false false false false 1 false false false false 0 0 6.       Pension and Other Postretirement Benefits The following tables provide the components of net periodic benefit cost for our company-sponsored qualified and non-qualified defined benefit pension plans and other postretirement benefit plans:<div><table style="border-collapse:collapse;margin-top:20px;"><tr style="height: 20px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;"> </td><td style="width: 10px; text-align:left;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td colspan="10" style="width: 375px; border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:375px;">Three Months Ended September 30,</td></tr><tr style="height: 20px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;"> </td><td style="width: 10px; text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:75px;"> </td><td style="width: 10px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:75px;"> </td><td style="width: 10px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:15px;"> </td><td colspan="4" style="width: 175px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:175px;">Other Postretirement</td></tr><tr style="height: 20px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;"> </td><td style="width: 10px; text-align:left;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td colspan="4" style="width: 175px; border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:175px;">Pension Benefits</td><td style="width: 10px; text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td colspan="4" style="width: 175px; border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:175px;">Benefits</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Thousands</td><td style="width: 10px; text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:75px;">2010</td><td style="width: 10px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:75px;">2009</td><td style="width: 10px; text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:75px;">2010</td><td style="width: 10px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:75px;">2009</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Service cost</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 1,435</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 1,472</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 156</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 147</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Interest cost</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 4,517</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 4,474</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 343</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 405</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Expected return on plan assets</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> (4,528)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> (3,783)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> -</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> -</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Amortization of loss</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 2,028</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 1,786</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 7</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 5</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Amortization of prior service cost</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> (270)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 307</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 50</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 50</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Amortization of transition obligation</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> -</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> -</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 103</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 103</td></tr><tr style="height: 20px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;">Net periodic benefit cost</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 3,182</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 4,256</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 659</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 710</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Amount allocated to construction</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> (897)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> (1,220)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> (231)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> (233)</td></tr><tr style="height: 21px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;">Net amount charged to expense</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:right;border-color:#000000;min-width:75px;"> 2,285</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:right;border-color:#000000;min-width:75px;"> 3,036</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:right;border-color:#000000;min-width:75px;"> 428</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:right;border-color:#000000;min-width:75px;"> 477</td></tr><tr style="height: 21px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;"> </td><td style="width: 10px; text-align:left;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:double;border-top-width:3px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:double;border-top-width:3px;text-align:left;border-color:#000000;min-width:75px;"> </td><td style="width: 10px; text-align:left;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:double;border-top-width:3px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:double;border-top-width:3px;text-align:left;border-color:#000000;min-width:75px;"> </td><td style="width: 10px; text-align:left;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:double;border-top-width:3px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:double;border-top-width:3px;text-align:left;border-color:#000000;min-width:75px;"> </td><td style="width: 10px; text-align:left;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:double;border-top-width:3px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:double;border-top-width:3px;text-align:left;border-color:#000000;min-width:75px;"> </td></tr><tr style="height: 20px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;"> </td><td style="width: 10px; text-align:left;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td colspan="10" style="width: 375px; border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:375px;">Nine Months Ended September 30,</td></tr><tr style="height: 20px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;"> </td><td style="width: 10px; text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:75px;"> </td><td style="width: 10px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:75px;"> </td><td style="width: 10px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:15px;"> </td><td colspan="4" style="width: 175px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:175px;">Other Postretirement</td></tr><tr style="height: 20px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;"> </td><td style="width: 10px; text-align:left;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td colspan="4" style="width: 175px; border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:175px;">Pension Benefits</td><td style="width: 10px; text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:15px;"> </td><td colspan="4" style="width: 175px; border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:175px;">Benefits</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Thousands</td><td style="width: 10px; text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:75px;">2010</td><td style="width: 10px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:75px;">2009</td><td style="width: 10px; text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:75px;">2010</td><td style="width: 10px; border-top-style:solid;border-top-width:1px;text-align:center;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:solid;border-bottom-width:1px;text-align:center;border-color:#000000;min-width:75px;">2009</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Service cost</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 4,981</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 4,799</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 468</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 442</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Interest cost</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 13,500</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 13,458</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 1,028</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 1,218</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Expected return on plan assets</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> (13,655)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> (11,772)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> -</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> -</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Amortization of loss</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 5,564</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 5,103</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 22</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 13</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Amortization of prior service cost</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 140</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 918</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 148</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; text-align:right;border-color:#000000;min-width:75px;"> 148</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Amortization of transition obligation</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> -</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> -</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 309</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 309</td></tr><tr style="height: 20px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;">Net periodic benefit cost</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 10,530</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 12,506</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 1,975</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-top-style:solid;border-top-width:1px;text-align:right;border-color:#000000;min-width:75px;"> 2,130</td></tr><tr style="height: 20px"><td colspan="2" style="width: 320px; text-align:left;border-color:#000000;min-width:320px;">Amount allocated to construction</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> (2,797)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> (3,576)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> (646)</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-bottom-style:solid;border-bottom-width:1px;text-align:left;border-color:#000000;min-width:15px;"> </td><td style="width: 75px; border-bottom-style:solid;border-bottom-width:1px;text-align:right;border-color:#000000;min-width:75px;"> (697)</td></tr><tr style="height: 21px"><td style="width: 20px; text-align:left;border-color:#000000;min-width:20px;"> </td><td style="width: 300px; text-align:left;border-color:#000000;min-width:300px;">Net amount charged to expense</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:right;border-color:#000000;min-width:75px;"> 7,733</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:right;border-color:#000000;min-width:75px;"> 8,930</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:right;border-color:#000000;min-width:75px;"> 1,329</td><td style="width: 10px; text-align:right;border-color:#000000;min-width:10px;"> </td><td style="width: 15px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:left;border-color:#000000;min-width:15px;">$</td><td style="width: 75px; border-top-style:solid;border-top-width:1px;border-bottom-style:double;border-bottom-width:3px;text-align:right;border-color:#000000;min-width:75px;"> 1,433</td></tr></table></div>See Part II, Item 8., Note 7, in the 2009 Form 10-K for more information about our pension and other postretirement benefit plans. In addition to the company-sponsored defined benefit plans referred to above, we contribute to a multiemployer pension plan for our bargaining unit employees in accordance with our collective bargaining agreement, known as the Western States Office and Professional Employees International Union Pension Fund (Western States Plan).  The Western States Plan is managed by a board of trustees that includes equal representation from participating employers and labor unions. Contribution rates are established by collective bargaining agreements, and benefit levels are set by the board of trustees based on the advice of an independent actuary regarding the level of benefits that agreed-upon contributions are expected to support.  As of January 1, 2010, the Western States Plan had an accumulated funding deficiency for the current plan year and remained in “critical status.” A plan is considered to be in critical status if its funded status is 65 percent or less. Federal law requires pension plans in critical status to adopt a rehabilitation plan designed to restore the financial health of the plan. Rehabilitation plans may specify benefit reductions, contribution surcharges, or a combination of the two. We made contributions totaling $0.3 million to the Western States Plan for both the nine months ended September 30, 2010 and 2009.  The Western States Plan board of trustees imposed a 5 percent contribution surcharge to participating employers, including NW Natural, beginning in August 2009, which increased to a 10 percent contribution surcharge beginning January 2010.  The board of trustees also adopted a rehabilitation plan that reduced benefit accrual rates and adjustable benefits for active employee participants and increased future employer contribution rates.  These changes are expected to improve the funding status of the plan.  Contribution surcharges above 10 percent will be assessed to employer participants, but these higher surcharges will not go into effect for NW Natural until its next collective bargaining agreement, which is expected to be no earlier than June 1, 2014.  Under the terms of our current collective bargaining agreement, which became effective in July 2009, we can withdraw from the Western States Plan at any time.  However, if we withdraw and the plan is underfunded, we could be assessed a withdrawal liability.  We have no current intent to withdraw from the plan, so we have not recorded a withdrawal liability. Employer Pension Contributions In February 2010, we made a $10 million cash contribution to our qualified defined benefit pension plans, portions of which were for the 2009 and 2010 plan years, and additional contributions are expected for future years. We also continue to make cash contributions for our unfunded, non-qualified pension plans and other postretirement benefit plans. For more information see Part II, Item 8., Note 7, in the 2009 Form 10-K. 6.       Pension and Other Postretirement Benefits The following tables provide the components of net periodic benefit false false false us-types:textBlockItemType textblock Description containing the entire pension and other postretirement benefits disclosure as a single block of text. 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