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For bargaining employees, who are subject to the International Brotherhood of Electrical Workers Local 125 agreements, the Company contributes a stated amount per compensable hour plus this percentage of the employee’s base salary, whether or not the employee contributes to the 401k Plan.

No definition available.

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Company match, percentage of participating employee's base salary for employees hired post January 31, 2009.

No definition available.

Name:	por_CompanyMatchPost2008Hire
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Company match, percentage of participating employee's base salary for employees hired pre February 1, 2009.

No definition available.

Name:	por_CompanyMatchPre2009Hire
Namespace Prefix:	por_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Contributions to the HRAs provide for claims by retirees for qualified medical costs. For active bargaining employees, the participants’ accounts are credited with 100% of their earned time off accumulated at the time of retirement.

No definition available.

Name:	por_Contributiontohealthreimbursementaccountearnedtimeoff
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Contributions to the HRAs provide for claims by retirees for qualified medical costs. For active bargaining employees, the participants’ accounts are credited with 58% of the value of the employee’s accumulated sick time as of April 30, 2004.

No definition available.

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Period Type:	duration

The assumed health care cost trend rate for the current year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

No definition available.

Name:	por_DefinedBenefitPlanCurrentAnnualRateOfHealthCareCostIncrease
Namespace Prefix:	por_
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Balance Type:	na
Period Type:	duration

- Details

Name:	por_EmployeeBenefitsAbstract
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Period Type:	duration

The aggregate amount in accumulated other comprehensive income expected to be recognized as a component of net periodic benefit cost over the fiscal year that follows the most recent annual statement of financial position presented, consisting of the net actuarial loss for non-qualified benefits.

No definition available.

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The aggregate amount in accumulated other comprehensive income expected to be recognized as a component of net periodic benefit cost over the fiscal year that follows the most recent annual statement of financial position presented related to the net actuarial loss for pension benefits.

No definition available.

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No definition available.

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Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

This represents the current liability recognized in the balance sheet that is associated with other postretirement defined benefit plans (excluding pension plans).

No definition available.

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No definition available.

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Amount included in accumulated other comprehensive income (AOCI) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position, including gain (loss), prior service cost (credit), and transition asset (obligation).

No definition available.

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Postretirement Benefits

-URI http://asc.fasb.org/extlink&oid=6521376

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Benefits

-URI http://asc.fasb.org/extlink&oid=6506267

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Benefits

-URI http://asc.fasb.org/extlink&oid=6506309

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(6)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(5)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	duration

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

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Data Type:	xbrli:monetaryItemType
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The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (l)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Health Care Cost Trend Rate

-URI http://asc.fasb.org/extlink&oid=6514820

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The ultimate trend rate for health care costs.

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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Amount of discretionary contributions made by an employer to a defined contribution plan.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of cash or cash equivalents contributed by the entity to fund its pension plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585