Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Consolidated Balance Sheets
Ordinary stock, nominal value	$ 0.01	$ 0.01
Ordinary stock, authorized shares	1,000,000,000	1,000,000,000
Ordinary stock, issued shares	40,233,867	36,707,685
Ordinary stock, outstanding shares	40,233,867	36,707,685
Preferred stock, par value (in dollars per share)	$ 0.01
Preferred stock, authorized shares	100,000,000
Preferred stock, issued shares	0
Preferred stock, outstanding shares	0