Acquisitions - Schedule of Proforma Data (Details) - Tsugaru Holdings - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2018
Business Acquisition, Pro Forma Information [Abstract]
Pro forma total revenue	$ 118	$ 374
Pro forma total expenses	(150)	(419)
Pro forma net loss	(32)	(45)
Less: pro forma net loss attributable to noncontrolling interest	(19)	(202)
Pro forma net income (loss) attributable to Pattern Energy	$ (13)	$ 157

Business Acquisition, Pro Forma Expense

No definition available.

Name:	pegi_BusinessAcquisitionProFormaExpense
Namespace Prefix:	pegi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Business Acquisition, Pro Forma Net Income (Loss), Portion Attributable to Noncontrolling Interest

+ References

No definition available.

+ Details

Name:	pegi_BusinessAcquisitionProFormaNetIncomeLossPortionAttributabletoNoncontrollingInterest
Namespace Prefix:	pegi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Business Acquisition, Pro Forma Net Income (Loss), Portion Attributable to Parent

+ References

No definition available.

+ Details

Name:	pegi_BusinessAcquisitionProFormaNetIncomeLossPortionAttributabletoParent
Namespace Prefix:	pegi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionProFormaInformationAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionsProFormaRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=pegi_TsugaruHoldingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: