Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		9 Months Ended
	May 04, 2016	Apr. 08, 2016	Jul. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Shareholders' Equity
Net proceeds from sale of ordinary shares				$ 145,241	$ 27,262
Ordinary shares, par value (in dollars per share)				$ 0.00001		$ 0.00001
At-the-Market Agreement
Shareholders' Equity
Sale of ordinary shares (in shares)		770,000
Net proceeds from sale of ordinary shares		$ 14,300
At-the-Market Agreement | Average
Shareholders' Equity
Share price (in dollars per share)		$ 19.53
Prospectus supplement filed with SEC on April 28, 2016
Shareholders' Equity
Sale of ordinary shares (in shares)	5,479,750
Share price (in dollars per share)	$ 21.00
Net proceeds from sale of ordinary shares	$ 107,900
Ordinary shares, par value (in dollars per share)	$ 0.00001
Cantor Fitzgerald & Co | At-the-Market Agreement | Maximum
Shareholders' Equity
Net proceeds from sale of ordinary shares			$ 50,000
Sales agent and underwriter commission rate (as a percent)			3.00%