Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	$ 142,330	$ 127,332
Available-for-sale debt securities	26,017	25,708	$ 60,659
Deferred compensation plan liabilities	(142,330)	(127,332)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	142,330	127,332
Available-for-sale debt securities	26,017	25,708
Deferred compensation plan liabilities	(142,330)	(127,332)
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	(1,151)	(2,565)
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent purchase price liabilities	$ (66,187)	$ (54,391)