Fair Value Measurements - Summary of Fair Value Assets Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets
Assets fair value	$ 359,062	$ 429,285
Money market funds
Assets
Assets fair value	130,176	100,441
Fair Value Measurements on Recurring Basis | Level 1
Assets
Assets fair value	130,176	100,441
Fair Value Measurements on Recurring Basis | Level 2
Assets
Assets fair value	228,886	328,844
Fair Value Measurements on Recurring Basis | Money market funds | Level 1
Assets
Assets fair value	130,176	100,441
U.S. government agency obligations
Assets
Assets fair value	107,657	134,055
U.S. government agency obligations | Fair Value Measurements on Recurring Basis | Level 2
Assets
Assets fair value	107,657	134,055
Corporate securities
Assets
Assets fair value	121,229	194,789
Corporate securities | Fair Value Measurements on Recurring Basis | Level 2
Assets
Assets fair value	$ 121,229	$ 194,789