Basis of Presentation and Summary of Significant Accounting Policies - Summary of Cash Reported in Condensed Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 443,693	$ 246,122
Restricted cash included in prepaid expenses and other current assets	364
Restricted cash included in restricted cash and other	1,856	2,143
Total cash, cash equivalents and restricted cash shown in the consolidated statements of cash flows	$ 445,913	$ 248,265	$ 347,113	$ 224,857