Investments and Fair Value Measurements - Summary of Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Summary of Investments [Abstract]
Cost	$ 252,707	$ 160,761
Gross unrealized gains	1,447	75
Gross unrealized losses	(10)	(32)
Estimated fair value	254,144	160,804
Securities with Maturity of One Year or Less [Member]
Summary of Investments [Abstract]
Cost	199,557	144,649
Gross unrealized gains	863	70
Gross unrealized losses	(6)	(29)
Estimated fair value	200,414	144,690
Securities with Maturity of More than One Year [Member]
Summary of Investments [Abstract]
Cost	53,150	16,112
Gross unrealized gains	584	5
Gross unrealized losses	(4)	(3)
Estimated fair value	53,730	16,114
Corporate Debt Securities [Member] | Securities with Maturity of One Year or Less [Member]
Summary of Investments [Abstract]
Cost	81,143	105,679
Gross unrealized gains	374	40
Gross unrealized losses	(1)	(23)
Estimated fair value	81,516	105,696
Corporate Debt Securities [Member] | Securities with Maturity of More than One Year [Member]
Summary of Investments [Abstract]
Cost	30,878	2,033
Gross unrealized gains	354	5
Estimated fair value	31,232	2,038
Debt Securities Issued by U.S. Government Agencies [Member] | Securities with Maturity of One Year or Less [Member]
Summary of Investments [Abstract]
Cost	118,414	38,970
Gross unrealized gains	489	30
Gross unrealized losses	(5)	(6)
Estimated fair value	118,898	38,994
Debt Securities Issued by U.S. Government Agencies [Member] | Securities with Maturity of More than One Year [Member]
Summary of Investments [Abstract]
Cost	22,272	14,079
Gross unrealized gains	230
Gross unrealized losses	(4)	(3)
Estimated fair value	$ 22,498	$ 14,076