v3.4.0.3
Document and Entity Information - shares
6 Months Ended
Mar. 31, 2016
Apr. 30, 2016
Document Information [Line Items]    
Entity Registrant Name WGL Holdings Inc.  
Entity Central Index Key 0001103601  
Document Type 10-Q  
Document Period End Date Mar. 31, 2016  
Amendment Flag false  
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --09-30  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   50,338,313
Washington Gas Light Company    
Document Information [Line Items]    
Entity Registrant Name Washington Gas Light Company  
Entity Central Index Key 0000104819  
Document Type 10-Q  
Document Period End Date Mar. 31, 2016  
Amendment Flag false  
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --09-30  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   0