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Long-Term Debt - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2022
Dec. 31, 2021
Debt Instrument [Line Items]    
Document Period End Date Mar. 31, 2022  
Long-term debt including current maturities $ 618,600 $ 568,800
Debt Instrument, Unused Borrowing Capacity, Amount 250,000  
Short-term borrowing $ 140,865 221,634
Uncollateralized Senior Note Due December Two Thousand Thirty Four [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 2.98%  
Term Note Due January Two Thousand Twenty [Member]    
Debt Instrument [Line Items]    
Long-term debt including current maturities $ 70,000 70,000
3.48% note, due May 31, 2038 [Member]    
Debt Instrument [Line Items]    
Long-term debt including current maturities 50,000 50,000
3.25% note, due April 30, 2032 [Member]    
Debt Instrument [Line Items]    
Long-term debt including current maturities 70,000 70,000
Aggregated Unfunded Commitments [Member]    
Debt Instrument [Line Items]    
Long-term debt including current maturities 0  
Equipment Security Note    
Debt Instrument [Line Items]    
Long-term debt including current maturities $ 9,165 $ 9,378
Debt Instrument, Interest Rate, Stated Percentage 2.46%  
Equipment Security Note | Marlin Gas Services [Member]    
Debt Instrument [Line Items]    
Long-term debt including current maturities $ 9,600  
Uncollateralized Senior Note Due March 15, 2042    
Debt Instrument [Line Items]    
Long-term debt including current maturities $ 50,000  
Debt Instrument, Interest Rate, Stated Percentage 2.95%  
Aggregate Shelf Agreements [Member]    
Debt Instrument [Line Items]    
Long-term debt including current maturities $ 270,000  
MetLife [Member]    
Debt Instrument [Line Items]    
Senior notes [1] 150,000  
Long-term debt including current maturities [1] 50,000  
Debt Instrument, Unused Borrowing Capacity, Amount [1] 100,000  
MetLife [Member] | Uncollateralized Senior Note Due March 15, 2042    
Debt Instrument [Line Items]    
Long-term debt including current maturities 50,000  
Prudential [Member]    
Debt Instrument [Line Items]    
Long-term debt including current maturities [1] 220,000  
Debt Instrument, Unused Borrowing Capacity, Amount [1] 150,000  
Maximum [Member] | Aggregate Shelf Agreements [Member]    
Debt Instrument [Line Items]    
Senior notes 520,000  
Maximum [Member] | Prudential [Member]    
Debt Instrument [Line Items]    
Senior notes [1] $ 370,000  
[1] (1) The Prudential and MetLife Shelf Agreements expire in April 2023 and May 2023, respectively.