Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	$ 133,478	$ 127,332
Available-for-sale debt securities	22,393	25,708	$ 60,659
Deferred compensation plan liabilities	(133,478)	(127,332)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	133,478	127,332
Available-for-sale debt securities	22,393	25,708
Deferred compensation plan liabilities	(133,478)	(127,332)
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	(1,299)	(2,565)
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent purchase price liabilities	$ (54,230)	$ (54,391)