Convertible Preferred Stock - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	9 Months Ended
Apr. 30, 2017	May 31, 2017	Sep. 30, 2018
Equity [Abstract]
Preferred stock, convertible, conversion price	$ 10.1338	$ 9.8329
Deemed dividend related to change in conversion rate of Series D convertible preferred stock			$ 1.1
Incremental common shares attributable to dilutive effect of conversion of preferred stock			253,361

Number of shares of preferred stock issued as dividends during the period. Excludes stock splits.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Name:	us-gaap_PreferredStockDividendsShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration