Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Options (Details)

v3.8.0.1
Summary of Significant Accounting Policies - Options (Details) - £ / shares
 2 Months Ended 6 Months Ended 12 Months Ended
Feb. 28, 2018
Dec. 31, 2015
Dec. 31, 2017
Dec. 31, 2016
Jun. 30, 2015
Number of options granted (in shares)   0 29,924,787 19,404,373 21,779,577
Nominal value of ordinary shares £ 0.001   £ 0.001 £ 0.001  
Exercise price determined by reference to the market value of an ADS at the date of grant          
Number of options granted (in shares) 9,994,656        
Exercise price equal to the nominal value of the ordinary shares          
Number of options granted (in shares) 6,555,900