Fair Value Measurements, Cash Equivalents and Marketable Securities - Activity In Level 3 Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Initial fair value of contingent consideration at acquisition date	$ 0	$ 1,135	$ 0	$ 1,135
Fair Value, Measurements, Recurring
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Initial fair value of contingent consideration at acquisition date	1,175		1,175			$ 1,365
Fair Value, Measurements, Recurring | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Initial fair value of contingent consideration at acquisition date	1,175		1,175			1,365
Redeemable Noncontrolling Interest | Fair Value, Measurements, Recurring | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value — beginning of period	45,500	46,500	49,600	41,800
Initial fair value of contingent consideration at acquisition date					$ 0	0	$ 0	$ 0
Increase (decrease) in fair value	6,186	922	3,159	5,944
Net loss for the period	(1,286)	(622)	(2,359)	(944)
Fair value — end of period	50,400	46,800	50,400	46,800
Contingent Consideration | Fair Value, Measurements, Recurring | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value — beginning of period	1,175	0	1,365	0
Initial fair value of contingent consideration at acquisition date					$ 0	$ 0	$ 1,065	$ 1,065
Increase (decrease) in fair value	0	0	(190)	0
Net loss for the period	0	0	0	0
Fair value — end of period	$ 1,175	$ 1,065	$ 1,175	$ 1,065