XML 148 R107.htm IDEA: XBRL DOCUMENT v3.8.0.1
Common Stock Common Stock (Dividends Declared) (Details) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dividend Restrictions [Line Items]        
Amount Available For Dividend Distribution Without Affecting Covenants   $ 97,600,000    
Maximum Dividend Increase Allowed Per Merger Agreement   $ 0.06    
Dividends declared per common share   $ 1.43 $ 1.37 $ 1.32
Avista Utilities [Member]        
Dividend Restrictions [Line Items]        
Regulatory Restrictions, Maximum Debt to Equity   40.00%    
Subsequent Event [Member]        
Dividend Restrictions [Line Items]        
Dividends declared per common share $ 1.49