Annual report pursuant to Section 13 and 15(d)

Schedule II - Valuation and Qualifying Accounts (Details)

v3.20.4
Schedule II - Valuation and Qualifying Accounts (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]        
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount $ 2,668 $ 2,448 $ 2,440 $ 3,351
Valuation Allowances and Reserves, Charged to Cost and Expense 567 752 157  
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction 5,098 4,083 4,692  
SEC Schedule, 12-09, Allowance, Credit Loss [Member]        
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]        
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount 1,268 1,316 1,290 2,540
Valuation Allowances and Reserves, Charged to Cost and Expense 567 752 122  
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction [1] 615 726 1,372  
Allowance for revenue adjustments [Member]        
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]        
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount 1,005 737 [2] 755 [2] 451 [2]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Other Account 4,751 3,339 3,624  
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction [3] 4,483 3,357 3,320  
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member]        
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]        
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount 395 395 395 $ 360
Valuation Allowances and Reserves, Charged to Cost and Expense $ 0 $ 0 $ 35  
[1] Represents uncollectible accounts written off, net of recoveries.
[2] Represents an allowance for revenue adjustments to accounts receivable resulting from future billing rate changes.
[3] Represents adjustments to billed accounts receivable