Organization and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands		1 Months Ended
	Oct. 07, 2015 USD ($) shares	Sep. 30, 2015 $ / shares	Dec. 31, 2015 $ / shares	Sep. 30, 2015 £ / shares	Dec. 31, 2014 $ / shares
Organization And Basis Of Presentation [Line Items]
Ordinary shares no par value
preferred shares no par value
Share split ratio		5.913
Preferred stock, par value | (per share)			$ 0	£ 0.01	$ 0
Common stock, par value | (per share)			$ 0	£ 0.01	$ 0
Ordinary Shares | IPO
Organization And Basis Of Presentation [Line Items]
Issuance of shares, net (in shares) | shares	7,876,195
Proceeds from issuance of ordinary shares | $	$ 157,534