Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities - Summary of Active Derivative Instruments (Details)

v3.10.0.1
Derivative Instruments and Hedging Activities - Summary of Active Derivative Instruments (Details)
Sep. 30, 2018
USD ($)
MMBTU
$ / MMBTU
Dec. 31, 2017
USD ($)
Designated | Interest Rate Swap June 2033    
Derivative [Line Items]    
Term of contract 15 years  
Fixed interest rate 3.19%  
Initial Notional Amount $ 10,000,000  
Designated | Interest Rate Swap - December 2027    
Derivative [Line Items]    
Term of contract 10 years  
Fixed interest rate 4.74%  
Initial Notional Amount $ 14,100,000  
Designated | Interest Rate Swap - December 2038    
Derivative [Line Items]    
Term of contract 15 years  
Fixed interest rate 3.26%  
Initial Notional Amount $ 14,084,000  
Designated | Interest Rate Swap - February 2023    
Derivative [Line Items]    
Term of contract 7 years  
Fixed interest rate 2.19%  
Initial Notional Amount $ 20,746,000  
Designated | Interest Rate Swap - June 2028 - Contract 1    
Derivative [Line Items]    
Term of contract 8 years  
Fixed interest rate 3.70%  
Initial Notional Amount $ 14,643,000  
Designated | Interest Rate Swap - June 2028 - Contract 2    
Derivative [Line Items]    
Term of contract 8 years  
Fixed interest rate 3.70%  
Initial Notional Amount $ 10,734,000  
Designated | Interest Rate Swap - March 2020 - Contract 1    
Derivative [Line Items]    
Term of contract 8 years  
Fixed interest rate 1.71%  
Initial Notional Amount $ 9,665,000  
Designated | Interest Rate Swap - March 2020 - Contract 2    
Derivative [Line Items]    
Term of contract 8 years  
Fixed interest rate 1.71%  
Initial Notional Amount $ 7,085,000  
Designated | Interest Rate Swap - February 2021    
Derivative [Line Items]    
Term of contract 15 years  
Fixed interest rate 5.30%  
Initial Notional Amount $ 3,256,000  
Designated | Interest Rate Swap - March 2024    
Derivative [Line Items]    
Term of contract 15 years 6 months  
Fixed interest rate 5.40%  
Initial Notional Amount $ 13,081,000  
Not Designated | Interest Rate Swap - December 2020    
Derivative [Line Items]    
Term of contract 3 years  
Fixed interest rate 2.46%  
Initial Notional Amount $ 17,100,000  
Not Designated | Commodity Contract - April 2019    
Derivative [Line Items]    
Term of contract 1 year  
Price | $ / MMBTU 2.84  
Nonmonetary notional amount (in MMBtus) | MMBTU 323,390  
Not Designated | Commodity Contract - April 2020    
Derivative [Line Items]    
Term of contract 1 year  
Price | $ / MMBTU 2.68  
Nonmonetary notional amount (in MMBtus) | MMBTU 437,004  
Not Designated | Commodity Contract - April 2021    
Derivative [Line Items]    
Term of contract 1 year  
Price | $ / MMBTU 2.70  
Nonmonetary notional amount (in MMBtus) | MMBTU 435,810  
Not Designated | Other liabilities | Interest make-whole provisions    
Derivative [Line Items]    
Liability derivatives $ 1,488,000 $ 0