Preferred Stock - Adjustment to the Carrying Value Redeemable Convertible Preferred Stock (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Preferred stock
Accretion of preferred stock to redemption value	$ 159,453	$ (3,323)	$ 199,492	$ 8,324

Amount of decrease to net income for accretion of temporary equity to its redemption value to derive net income apportioned to common stockholders.

No definition available.

Name:	us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration