Fair Value Disclosure - Schedule of Financial Assets Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Restricted cash	$ 1,854
Fair Value		$ 42,146
Total assets measured and recorded at fair value	517,333	197,710
Level 1
Assets:
Restricted cash	1,854
Total assets measured and recorded at fair value	517,333	155,564
Level 2
Assets:
Total assets measured and recorded at fair value		42,146
Cash
Assets:
Cash and cash equivalents	463,820	147,221
Cash | Level 1
Assets:
Cash and cash equivalents	463,820	147,221
Money Market Fund
Assets:
Cash and cash equivalents	51,659	8,343
Money Market Fund | Level 1
Assets:
Cash and cash equivalents	$ 51,659	8,343
Corporate Bonds and Commercial Paper
Assets:
Fair Value		37,151
Corporate Bonds and Commercial Paper | Level 2
Assets:
Fair Value		37,151
U.S. Government Securities
Assets:
Fair Value		4,995
U.S. Government Securities | Level 2
Assets:
Fair Value		$ 4,995