Silvercrest Asset Management Group LLC Quarterly report pursuant to Section 13 or 15(d)

Investments and Fair Value Measurements - Schedule of Inputs Used in Fair Value Measurement of Estimated Contingent Consideration (Detail) - Level 3 $ in Thousands	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity consideration for SLP acquired	$ 18,588	$ 16,402	$ 15,921
Forecasted Growth Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input of estimated contingent consideration	17.2	16.4
Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input of estimated contingent consideration	11.9	11.7