Investments In Marketable Securities - Summary of Cost, Gross Unrealized Holding Gains and Losses and Fair Value of Available-for-sale Investments by Types and Classes of Security (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Amortized Cost	$ 141,416
Available-for-sale investment securities, Gross Unrealized Gains	228
Available-for-sale investment securities, Fair Market Value	141,644
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Amortized Cost	97,704
Available-for-sale investment securities, Gross Unrealized Gains	155
Available-for-sale investment securities, Fair Market Value	$ 97,859
Commercial Paper | Maximum
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Maturity (in years)	1 year
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Amortized Cost	$ 34,712
Available-for-sale investment securities, Gross Unrealized Gains	68
Available-for-sale investment securities, Fair Market Value	$ 34,780
Corporate Debt Securities | Maximum
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Maturity (in years)	1 year
Government-Sponsored Enterprise Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Amortized Cost	$ 9,000
Available-for-sale investment securities, Gross Unrealized Gains	5
Available-for-sale investment securities, Fair Market Value	$ 9,005
Government-Sponsored Enterprise Securities | Maximum
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Maturity (in years)	1 year