Summary of Significant Accounting Policies - Summary of Impact of Adopting ASC 230 on Unaudited Condensed Statement of Cash Flows (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Net cash provided by (used in) investing activities		$ 57,394	$ (117,090)
Net increase in cash, cash equivalents and restricted cash		12,660	29,204	[1]
Cash, cash equivalents, and restricted cash at beginning of period		48,915	10,647	[1]
Cash, cash equivalents, and restricted cash at end of period		$ 61,575	39,851	[1]
As Originally Reported | ASC 2016-18
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Change in restricted cash			(394)
Net cash provided by (used in) investing activities			(117,484)
Net increase in cash, cash equivalents and restricted cash	[1]		28,810
Cash, cash equivalents, and restricted cash at beginning of period	[1]		10,601
Cash, cash equivalents, and restricted cash at end of period	[1]		39,411
Adjustments | ASC 2016-18
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Change in restricted cash			394
Net cash provided by (used in) investing activities			394
Net increase in cash, cash equivalents and restricted cash	[1]		394
Cash, cash equivalents, and restricted cash at beginning of period	[1]		46
Cash, cash equivalents, and restricted cash at end of period	[1]		$ 440

[1] For the nine months ended September 30, 2017, this line item, as originally reported, excluded restricted cash.