XML 54 R39.htm IDEA: XBRL DOCUMENT v3.20.4
Significant Accounting Policies (Activity in Allowance for Doubtful Accounts) (Parenthetical) (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2020
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Allowance For Doubtful Accounts Receivable [Line Items]                      
Net service revenues $ 195,996 $ 193,987 $ 184,576 $ 190,216 $ 192,376 $ 168,993 $ 148,915 $ 138,507 $ 764,775 $ 648,791 $ 516,647
Accounting Standards Update 2014-09 [Member]                      
Allowance For Doubtful Accounts Receivable [Line Items]                      
Net service revenues                     $ 18,000