XML 83 R71.htm IDEA: XBRL DOCUMENT v3.8.0.1
North Dakota Public Service Commission (NDPSC) (Details 3) - NDPSC - USD ($)
$ in Millions
Mar. 09, 2018
Mar. 01, 2018
Feb. 14, 2018
Sep. 06, 2017
Jul. 21, 2017
Natural gas rate proceeding          
Public Utilities, General Disclosures [Line Items]          
Public utilities, requested rate increase (decrease), amount         $ 5.9
Public utilities, requested rate increase (decrease), percentage         5.40%
Public utilities, interim rate increase (decrease), amount       $ 4.6  
Public utilities, interim rate increase (decrease), percentage       4.20%  
Natural gas rate proceeding | Tax Cuts and Jobs Act          
Public Utilities, General Disclosures [Line Items]          
Public utilities interm rate increase (decrese) revised     $ 2.7    
Public utilities, requested rate increase (decrease), amended, amount   $ 3.6      
Electric rate proceeding | Tax Cuts and Jobs Act          
Public Utilities, General Disclosures [Line Items]          
Public utilities, requested rate increase (decrease), amount $ (7.2)        
Public utilities, requested rate increase (decrease), percentage (3.90%)