Document And Entity Information - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Feb. 14, 2019
Jun. 29, 2018
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2018    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2018    
Entity Registrant Name Green Plains Inc.    
Entity Central Index Key 0001309402    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   41,039,553  
Entity Well-known Seasoned Issuer No    
Entity Public Float     $ 711.2
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Trading Symbol gpre    
Entity Emerging Growth Company false    
Entity Small Business false    
Entity Shell Company false