XML 110 R77.htm IDEA: XBRL DOCUMENT v3.10.0.1
Acquisitions and Dispositions - Southern Power Narrative (Details) - USD ($)
$ in Thousands
1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended 36 Months Ended
May 25, 2018
May 20, 2018
May 31, 2018
Jun. 30, 2018
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2017
Business Acquisition [Line Items]                  
Construction work in progress       $ 6,947,000 $ 6,947,000       $ 6,904,000
Sale of SPSH noncontrolling interests         1,283,000        
Assets subject to lien       112,777,000 112,777,000       111,005,000
SOUTHERN POWER CO                  
Business Acquisition [Line Items]                  
Construction work in progress       771,000 771,000       511,000
Sale of SPSH noncontrolling interests     $ 511,000            
Repayments of debt     770,000            
Repayments of capital     250,000   250,000 $ 0      
Assets subject to lien       15,428,000 15,428,000       $ 15,206,000
SOUTHERN POWER CO | Series of Construction Projects                  
Business Acquisition [Line Items]                  
Construction work in progress       353,000 353,000        
SOUTHERN POWER CO | Minimum | Series of Construction Projects                  
Business Acquisition [Line Items]                  
Estimated future construction payments       520,000 520,000        
SOUTHERN POWER CO | Maximum | Series of Construction Projects                  
Business Acquisition [Line Items]                  
Estimated future construction payments       590,000 590,000        
Wind Generating Facility | Scenario, Forecast | SOUTHERN POWER CO                  
Business Acquisition [Line Items]                  
Project qualification for production tax credits, percentage             80.00% 100.00%  
Disposal Group, Held-for-sale, Not Discontinued Operations | Florida Plants | SOUTHERN POWER CO                  
Business Acquisition [Line Items]                  
Proceeds from sale of equity method investments     195,000            
Decrease in consideration per day between end of fiscal year and closing     110            
Increase in consideration per day if closing is prior to end of fiscal year     $ 110            
Pre-tax impairment charge       119,000 119,000        
After tax impairment charge       $ 89,000 88,000        
SP Solar Holdings I, LP | SOUTHERN POWER CO                  
Business Acquisition [Line Items]                  
Limited liability company or limited partnership, members or limited partners, ownership interest   33.00% 33.00% 33.00%          
Proceeds from sale of equity method investments $ 1,200,000                
Common Stockholders' Equity                  
Business Acquisition [Line Items]                  
Sale of SPSH noncontrolling interests         (407,000)        
Senior Lien [Member] | SOUTHERN POWER CO | Mankato                  
Business Acquisition [Line Items]                  
Assets subject to lien       $ 475,000 $ 475,000