Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Narrative (Details)

v3.21.2
Fair Value Measurements - Narrative (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Sep. 30, 2021
Dec. 31, 2020
Assets and liabilities measured at fair value on a recurring basis      
Marketable securities in deferred compensation plan   $ 2,616 $ 3,027
Fair value measurement on a recurring basis | Deferred compensation plan | Trustees and Management      
Assets and liabilities measured at fair value on a recurring basis      
Maximum percentage of participants' compensation which is deferrable 100.00%    
Marketable securities in deferred compensation plan   $ 2,600