Amount of subscription receivable from investors who have been allocated nonredeemable preferred stock or preferred stock redeemable solely at the option of the issuer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65888546&loc=d3e21300-112643

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_PreferredStockSharesSubscribedButUnissuedSubscriptionsReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Consolidated Statements of Redeemable Convertible Preferred Shares and Shareholder's (Deficit) Equity (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common stock, issuance cost	$ 8,300
Series A-2 Redeemable Convertible Preferred Shares [Member]
Preferred shares, issuance cost			$ 36
Preferred shares, subscription receivable			$ 5,293
Series A-3 Redeemable Convertible Preferred Shares [Member]
Preferred shares, issuance cost		$ 332
Preferred shares, subscription receivable		22,850
Series B Redeemable Convertible Preferred Shares [Member]
Preferred shares, issuance cost	$ 1,800	$ 38