Fair Value Measurements - Financial Assets And Liabilities Measured At Fair Value On Recurring Basis (Details) - Fair value, measurements, recurring - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Acquisition-related contingent consideration—current
Liabilities:
Fair value of financial liabilities measured on recurring basis	$ 9,142	$ 6,534
Acquisition-related contingent consideration—noncurrent
Liabilities:
Fair value of financial liabilities measured on recurring basis	32,915	23,123
Money market funds
Assets:
Fair value of financial assets measured on recurring basis	638,966	427,033
Level 1 Inputs | Acquisition-related contingent consideration—current
Liabilities:
Fair value of financial liabilities measured on recurring basis	0	0
Level 1 Inputs | Acquisition-related contingent consideration—noncurrent
Liabilities:
Fair value of financial liabilities measured on recurring basis	0	0
Level 1 Inputs | Money market funds
Assets:
Fair value of financial assets measured on recurring basis	638,966	427,033
Level 2 Inputs | Acquisition-related contingent consideration—current
Liabilities:
Fair value of financial liabilities measured on recurring basis	0	0
Level 2 Inputs | Acquisition-related contingent consideration—noncurrent
Liabilities:
Fair value of financial liabilities measured on recurring basis	0	0
Level 2 Inputs | Money market funds
Assets:
Fair value of financial assets measured on recurring basis	0	0
Level 3 Inputs | Acquisition-related contingent consideration—current
Liabilities:
Fair value of financial liabilities measured on recurring basis	9,142	6,534
Level 3 Inputs | Acquisition-related contingent consideration—noncurrent
Liabilities:
Fair value of financial liabilities measured on recurring basis	32,915	23,123
Level 3 Inputs | Money market funds
Assets:
Fair value of financial assets measured on recurring basis	$ 0	$ 0