Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Level 2
Business Acquisition [Line Items]
Fair value of convertible notes	$ 145,962	$ 130,510

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

No definition available.

Name:	us-gaap_ConvertibleDebtFairValueDisclosures
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant