Investments and Fair Value Measurements - Summary of Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Summary of Investments [Abstract]
Cost	$ 277,541	$ 160,761
Gross unrealized gains	1,034	75
Gross unrealized losses	(593)	(32)
Estimated fair value	277,982	160,804
Securities with Maturity of One Year or Less [Member]
Summary of Investments [Abstract]
Cost	198,743	144,649
Gross unrealized gains	572	70
Gross unrealized losses	(414)	(29)
Estimated fair value	198,901	144,690
Securities with Maturity of More than One Year [Member]
Summary of Investments [Abstract]
Cost	78,798	16,112
Gross unrealized gains	462	5
Gross unrealized losses	(179)	(3)
Estimated fair value	79,081	16,114
Corporate Debt Securities [Member] | Securities with Maturity of One Year or Less [Member]
Summary of Investments [Abstract]
Cost	112,967	105,679
Gross unrealized gains	14	40
Gross unrealized losses	(414)	(23)
Estimated fair value	112,567	105,696
Corporate Debt Securities [Member] | Securities with Maturity of More than One Year [Member]
Summary of Investments [Abstract]
Cost	40,202	2,033
Gross unrealized gains	45	5
Gross unrealized losses	(175)
Estimated fair value	40,072	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	85,776	38,970
Gross unrealized gains	558	30
Gross unrealized losses		(6)
Estimated fair value	86,334	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	38,596	14,079
Gross unrealized gains	417
Gross unrealized losses	(4)	(3)
Estimated fair value	$ 39,009	$ 14,076