v3.8.0.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2018
May 07, 2018
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q1  
Trading Symbol PEGI  
Entity Registrant Name Pattern Energy Group Inc.  
Entity Central Index Key 0001561660  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   98,096,760