Convertible Preference Shares (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended			9 Months Ended
	Mar. 07, 2017	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Preferred Units [Line Items]
Preferred Stock, Value, Issued					$ (97)
Series 4 Convertible Preferred Stock
Preferred Units [Line Items]
Proceeds from issuance of convertible preference shares					$ 0	$ 95,000
Convertible Preferred Stock | Series 4 Convertible Preferred Stock
Preferred Units [Line Items]
Stock issued during period, convertible preferred (shares)	95,000				0
Proceeds from issuance of convertible preference shares	$ 95,000
Preferred Stock, Value, Issued	$ 90,123				$ (97)
Preferred Stock, Liquidation Preference Per Share	$ 1,000
Preferred Stock, Conversion Price, Preference Per Share	$ 10.00
Preferred Stock, Accretion Percentage, Preference	8.00%
Preferred Stock, Accretion Rate, Preference Per Share			$ 7.11		$ 7.40
Accretion on convertible preferred shares		$ 2,109		$ 1,948	$ 6,204	$ 4,365
Preferred Stock, Liquidation Preference, Value		$ 107,556			$ 107,556
Preferred Stock, Conversion Basis, Common Stock Class A Closing Trade Price					125.00%
Preferred Stock, Liquidation Preference Percentage Rate, Change of Control of the Company					7.00%