Related Parties - Additional Information (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
Related Party Transaction [Line Items]
Operating lease payments to related parties									$ 2,200	$ 2,400	$ 3,000
Revenue	$ 211,110	$ 238,389	$ 236,943	$ 277,455	$ 203,138	$ 239,790	$ 235,498	$ 269,998	963,897	948,424	922,003
CPA Firms
Related Party Transaction [Line Items]
Revenue									$ 159,400	$ 157,600	$ 154,000