Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Details)

v3.8.0.1
Income Taxes - Additional Information (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Tax Contingency [Line Items]      
Transition adjustment which reduced net deferred tax assets $ 1,300    
Federal statutory income tax rate 35.00% 35.00% 35.00%
Net operating loss for federal income tax purposes $ 4,100    
NOL expiring in 2033 if not utilized 90    
NOL expiring in 2034 if not utilized 804    
NOL expiring in 2035 if not utilized 478    
NOL expiring in 2036 if not utilized 1,700    
NOL expiring in 2037 if not utilized 1,000    
Subsidiaries [Member]      
Income Tax Contingency [Line Items]      
Net operating loss for federal income tax purposes $ 1,000 $ 3,000 $ 1,400
State [Member] | Corridor Public Holdings, Inc. And Corridor Private Holdings, Inc. [Member]      
Income Tax Contingency [Line Items]      
Blended state tax rate 3.78% 3.78% 2.82%
State [Member] | Missouri [Member] | Mowood Corridor, Inc. And Corridor MoGas [Member]      
Income Tax Contingency [Line Items]      
Blended state tax rate 5.00% 5.00% 5.00%