Annual report pursuant to Section 13 and 15(d)

Contingencies (Details)

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Contingencies (Details)
1 Months Ended 2 Months Ended 4 Months Ended 12 Months Ended
Jun. 20, 2019
USD ($)
Feb. 01, 2018
MMBTU / d
Jan. 01, 2018
MMBTU / d
Jun. 30, 2018
USD ($)
Jan. 31, 2018
MMBTU / d
Nov. 30, 2017
MMBTU / d
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Nov. 30, 2018
MMBTU / d
Mar. 31, 2018
USD ($)
Mar. 31, 2017
USD ($)
Contingencies                        
Revenues from contracts with customers             $ 3,940,558,000 $ 4,133,139,000 $ 3,018,685,000      
Production and ad valorem taxes             125,142,000 126,474,000 94,521,000      
Interest             (228,111,000) (286,743,000) (268,701,000)      
Accrued revenue             317,886,000 474,827,000        
Accounts receivable             46,419,000 51,073,000        
Natural gas sales                        
Contingencies                        
Revenues from contracts with customers             2,247,162,000 $ 2,287,939,000 $ 1,769,284,000      
Doddridge County, Tyler County and Ritchie County, West Virginia | Minimum                        
Contingencies                        
Settlement amount       $ 100,000                
SJGC | Settled Litigation                        
Contingencies                        
Settlement amount received             $ 82,000,000          
WGL                        
Contingencies                        
Natural gas long term purchase contract volume increase after specified events (in MMBtu)/day | MMBTU / d                   530,000    
Damages awarded $ 96,000,000                      
WGL | Pending Litigation                        
Contingencies                        
Damages sought                     $ 40,000,000 $ 30,000,000
WGL - Braxton, West Virginia                        
Contingencies                        
Natural gas long term purchase contract volume (in MMBtu)/day | MMBTU / d   200,000 500,000                  
WGL - Loudoun County, Virginia                        
Contingencies                        
Natural gas long term purchase contract volume increase after specified events (in MMBtu)/day | MMBTU / d                   330,000    
Potential Positive Outcome of Litigation | WGL                        
Contingencies                        
Natural gas long term purchase contract volume (in MMBtu)/day | MMBTU / d         500,000 600,000