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Share-based Payments - Summary of Principal Assumptions used for Valuation of Share Options (Details)
 12 Months Ended
Dec. 31, 2017
GBP (£)
shares
yr
Dec. 31, 2016
GBP (£)
shares
yr
Dec. 31, 2015
shares
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Number of options granted | shares 1,500,815 507,690 0
2016 Share Options | Grant Date Jun 30, 2016      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   69.05%  
Dividend yield   0.00%  
Risk-free investment rate   0.11%  
Fair value of option at grant date   £ 4.02  
Fair value of share at grant date   6.97  
Exercise price at date of grant   £ 4.00  
Lapse date   Jun. 30, 2026  
Expected option life (years) | yr   2.50  
Number of options granted | shares   270,690  
2016 Share Options | Grant Date Aug 22, 2016 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   67.92%  
Dividend yield   0.00%  
Risk-free investment rate   0.07%  
Fair value of option at grant date   £ 6.15  
Fair value of share at grant date   8.61  
Exercise price at date of grant   £ 2.80  
Lapse date   Aug. 22, 2026  
Expected option life (years) | yr   2.36  
Number of options granted | shares   12,500  
2016 Share Options | Grant Date Aug 22, 2016 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   67.92%  
Dividend yield   0.00%  
Risk-free investment rate   0.07%  
Fair value of option at grant date   £ 6.01  
Fair value of share at grant date   8.61  
Exercise price at date of grant   £ 3.00  
Lapse date   Aug. 22, 2026  
Expected option life (years) | yr   2.36  
Number of options granted | shares   37,500  
2016 Share Options | Grant Date Aug 22, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   67.92%  
Dividend yield   0.00%  
Risk-free investment rate   0.07%  
Fair value of option at grant date   £ 5.74  
Fair value of share at grant date   8.61  
Exercise price at date of grant   £ 3.40  
Lapse date   Aug. 22, 2026  
Expected option life (years) | yr   2.36  
Number of options granted | shares   25,000  
2016 Share Options | Grant Date Aug 22, 2016 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   67.92%  
Dividend yield   0.00%  
Risk-free investment rate   0.07%  
Fair value of option at grant date   £ 5.62  
Fair value of share at grant date   8.61  
Exercise price at date of grant   £ 3.60  
Lapse date   Aug. 22, 2026  
Expected option life (years) | yr   2.36  
Number of options granted | shares   11,250  
2016 Share Options | Grant Date Aug 22, 2016 Five      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   67.92%  
Dividend yield   0.00%  
Risk-free investment rate   0.07%  
Fair value of option at grant date   £ 5.62  
Fair value of share at grant date   8.61  
Exercise price at date of grant   £ 3.60  
Lapse date   Aug. 22, 2026  
Expected option life (years) | yr   2.36  
Number of options granted | shares   5,000  
2016 Share Options | Grant Date Aug 22, 2016 Six      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   67.92%  
Dividend yield   0.00%  
Risk-free investment rate   0.07%  
Fair value of option at grant date   £ 5.62  
Fair value of share at grant date   8.61  
Exercise price at date of grant   £ 3.60  
Lapse date   Aug. 22, 2026  
Expected option life (years) | yr   2.36  
Number of options granted | shares   37,500  
2016 Share Options | Grant Date Oct 28, 2016 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   68.38%  
Dividend yield   0.00%  
Risk-free investment rate   0.28%  
Fair value of option at grant date   £ 5.85  
Fair value of share at grant date   8.76  
Exercise price at date of grant   £ 3.40  
Lapse date   Oct. 28, 2026  
Expected option life (years) | yr   2.17  
Number of options granted | shares   12,500  
2016 Share Options | Grant Date Oct 28, 2016 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   68.38%  
Dividend yield   0.00%  
Risk-free investment rate   0.28%  
Fair value of option at grant date   £ 5.46  
Fair value of share at grant date   8.76  
Exercise price at date of grant   £ 4.00  
Lapse date   Oct. 28, 2026  
Expected option life (years) | yr   2.17  
Number of options granted | shares   50,000  
2016 Share Options | Grant Date Oct 28, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility   60.92%  
Dividend yield   0.00%  
Risk-free investment rate   0.06%  
Fair value of option at grant date   £ 5.22  
Fair value of share at grant date   9.19  
Exercise price at date of grant   £ 4.00  
Lapse date   Dec. 12, 2026  
Expected option life (years) | yr   0.50  
Number of options granted | shares   45,750  
2016 Share Options | Vesting Dates One | Grant Date Jun 30, 2016      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 12, 2016  
2016 Share Options | Vesting Dates One | Grant Date Aug 22, 2016 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Aug. 22, 2016  
2016 Share Options | Vesting Dates One | Grant Date Aug 22, 2016 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Aug. 22, 2016  
2016 Share Options | Vesting Dates One | Grant Date Aug 22, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Dec. 07, 2016  
2016 Share Options | Vesting Dates One | Grant Date Aug 22, 2016 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Mar. 01, 2017  
2016 Share Options | Vesting Dates One | Grant Date Aug 22, 2016 Five      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   May 01, 2017  
2016 Share Options | Vesting Dates One | Grant Date Aug 22, 2016 Six      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   May 16, 2017  
2016 Share Options | Vesting Dates One | Grant Date Oct 28, 2016 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 28, 2017  
2016 Share Options | Vesting Dates One | Grant Date Oct 28, 2016 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 28, 2016  
2016 Share Options | Vesting Dates One | Grant Date Oct 28, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Dec. 12, 2017  
2016 Share Options | Vesting Dates Two | Grant Date Jun 30, 2016      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 12, 2017  
2016 Share Options | Vesting Dates Two | Grant Date Aug 22, 2016 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Aug. 22, 2017  
2016 Share Options | Vesting Dates Two | Grant Date Aug 22, 2016 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Aug. 22, 2017  
2016 Share Options | Vesting Dates Two | Grant Date Aug 22, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Dec. 07, 2017  
2016 Share Options | Vesting Dates Two | Grant Date Aug 22, 2016 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Mar. 01, 2018  
2016 Share Options | Vesting Dates Two | Grant Date Aug 22, 2016 Five      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   May 01, 2018  
2016 Share Options | Vesting Dates Two | Grant Date Aug 22, 2016 Six      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   May 16, 2018  
2016 Share Options | Vesting Dates Two | Grant Date Oct 28, 2016 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 28, 2018  
2016 Share Options | Vesting Dates Two | Grant Date Oct 28, 2016 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 28, 2017  
2016 Share Options | Vesting Dates Two | Grant Date Oct 28, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Dec. 12, 2018  
2016 Share Options | Vesting Dates Three | Grant Date Jun 30, 2016      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 12, 2018  
2016 Share Options | Vesting Dates Three | Grant Date Aug 22, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Dec. 07, 2018  
2016 Share Options | Vesting Dates Three | Grant Date Aug 22, 2016 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Mar. 01, 2019  
2016 Share Options | Vesting Dates Three | Grant Date Aug 22, 2016 Five      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   May 01, 2019  
2016 Share Options | Vesting Dates Three | Grant Date Aug 22, 2016 Six      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   May 16, 2019  
2016 Share Options | Vesting Dates Three | Grant Date Oct 28, 2016 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 28, 2019  
2016 Share Options | Vesting Dates Three | Grant Date Oct 28, 2016 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 28, 2018  
2016 Share Options | Vesting Dates Three | Grant Date Oct 28, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Dec. 12, 2019  
2016 Share Options | Vesting Dates Four | Grant Date Jun 30, 2016      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 12, 2019  
2016 Share Options | Vesting Dates Four | Grant Date Aug 22, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Dec. 07, 2019  
2016 Share Options | Vesting Dates Four | Grant Date Aug 22, 2016 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Mar. 01, 2020  
2016 Share Options | Vesting Dates Four | Grant Date Aug 22, 2016 Five      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   May 01, 2020  
2016 Share Options | Vesting Dates Four | Grant Date Aug 22, 2016 Six      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   May 16, 2020  
2016 Share Options | Vesting Dates Four | Grant Date Oct 28, 2016 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Oct. 28, 2020  
2016 Share Options | Vesting Dates Four | Grant Date Oct 28, 2016 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates   Dec. 12, 2020  
2017 Share Options | Grant Date May 16, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 66.56%    
Dividend yield 0.00%    
Risk-free investment rate 0.12%    
Fair value of option at grant date £ 7.70    
Fair value of share at grant date 11.08    
Exercise price at date of grant £ 4.00    
Lapse date May 16, 2027    
Expected option life (years) | yr 2.63    
Number of options granted | shares 23,250    
2017 Share Options | Grant Date Sep 13, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 66.94%    
Dividend yield 0.00%    
Risk-free investment rate 0.27%    
Fair value of option at grant date £ 6.15    
Fair value of share at grant date 10.43    
Exercise price at date of grant £ 5.40    
Lapse date Sep. 13, 2027    
Expected option life (years) | yr 2.30    
Number of options granted | shares 14,690    
2017 Share Options | Grant Date Sep 14, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 66.97%    
Dividend yield 0.00%    
Risk-free investment rate 0.36%    
Fair value of option at grant date £ 6.08    
Fair value of share at grant date 10.34    
Exercise price at date of grant £ 5.40    
Lapse date Sep. 14, 2027    
Expected option life (years) | yr 2.30    
Number of options granted | shares 25,000    
2017 Share Options | Grant Date Sep 14, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 66.97%    
Dividend yield 0.00%    
Risk-free investment rate 0.36%    
Fair value of option at grant date £ 6.08    
Fair value of share at grant date 10.34    
Exercise price at date of grant £ 5.40    
Lapse date Sep. 14, 2027    
Expected option life (years) | yr 2.30    
Number of options granted | shares 110,310    
2017 Share Options | Grant Date Sep 14, 2017 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 66.97%    
Dividend yield 0.00%    
Risk-free investment rate 0.36%    
Fair value of option at grant date £ 6.08    
Fair value of share at grant date 10.34    
Exercise price at date of grant £ 5.40    
Lapse date Sep. 14, 2027    
Expected option life (years) | yr 2.30    
Number of options granted | shares 12,500    
2017 Share Options | Grant Date Sep 14, 2017 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 66.97%    
Dividend yield 0.00%    
Risk-free investment rate 0.36%    
Fair value of option at grant date £ 3.90    
Fair value of share at grant date 10.34    
Exercise price at date of grant £ 10.80    
Lapse date Sep. 14, 2027    
Expected option life (years) | yr 2.30    
Number of options granted | shares 25,000    
2017 Share Options | Grant Date Sep 15, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 67.02%    
Dividend yield 0.00%    
Risk-free investment rate 0.44%    
Fair value of option at grant date £ 6.76    
Fair value of share at grant date 10.15    
Exercise price at date of grant £ 4.00    
Lapse date Sep. 15, 2027    
Expected option life (years) | yr 2.29    
Number of options granted | shares 45,750    
2017 Share Options | Grant Date Sep 15, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 67.02%    
Dividend yield 0.00%    
Risk-free investment rate 0.44%    
Fair value of option at grant date £ 10.11    
Fair value of share at grant date 10.15    
Exercise price at date of grant £ 0.04    
Lapse date Sep. 15, 2027    
Expected option life (years) | yr 2.29    
Number of options granted | shares 1,028,533    
2017 Share Options | Grant Date Sep 27, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 67.11%    
Dividend yield 0.00%    
Risk-free investment rate 0.47%    
Fair value of option at grant date £ 4.36    
Fair value of share at grant date 11.19    
Exercise price at date of grant £ 11.19    
Lapse date Sep. 27, 2027    
Expected option life (years) | yr 2.26    
Number of options granted | shares 37,500    
2017 Share Options | Grant Date Sep 27, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Volatility 67.11%    
Dividend yield 0.00%    
Risk-free investment rate 0.47%    
Fair value of option at grant date £ 4.36    
Fair value of share at grant date 11.19    
Exercise price at date of grant £ 11.19    
Lapse date Sep. 27, 2027    
Expected option life (years) | yr 2.26    
Number of options granted | shares 178,282    
2017 Share Options | Vesting Dates One | Grant Date May 16, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Oct. 28, 2017    
2017 Share Options | Vesting Dates One | Grant Date Sep 13, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 13, 2018    
2017 Share Options | Vesting Dates One | Grant Date Sep 14, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Mar. 06, 2018    
2017 Share Options | Vesting Dates One | Grant Date Sep 14, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2018    
2017 Share Options | Vesting Dates One | Grant Date Sep 14, 2017 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2018    
2017 Share Options | Vesting Dates One | Grant Date Sep 14, 2017 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2018    
2017 Share Options | Vesting Dates One | Grant Date Sep 15, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 15, 2018    
2017 Share Options | Vesting Dates One | Grant Date Sep 15, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 15, 2017    
2017 Share Options | Vesting Dates One | Grant Date Sep 27, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Mar. 20, 2018    
2017 Share Options | Vesting Dates One | Grant Date Sep 27, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 27, 2018    
2017 Share Options | Vesting Dates Two | Grant Date May 16, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Oct. 28, 2018    
2017 Share Options | Vesting Dates Two | Grant Date Sep 13, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 13, 2019    
2017 Share Options | Vesting Dates Two | Grant Date Sep 14, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Mar. 06, 2019    
2017 Share Options | Vesting Dates Two | Grant Date Sep 14, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2019    
2017 Share Options | Vesting Dates Two | Grant Date Sep 14, 2017 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2019    
2017 Share Options | Vesting Dates Two | Grant Date Sep 14, 2017 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2019    
2017 Share Options | Vesting Dates Two | Grant Date Sep 15, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 15, 2019    
2017 Share Options | Vesting Dates Two | Grant Date Sep 27, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Mar. 20, 2019    
2017 Share Options | Vesting Dates Two | Grant Date Sep 27, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 27, 2019    
2017 Share Options | Vesting Dates Three | Grant Date May 16, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Oct. 28, 2019    
2017 Share Options | Vesting Dates Three | Grant Date Sep 13, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 13, 2020    
2017 Share Options | Vesting Dates Three | Grant Date Sep 14, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Mar. 06, 2020    
2017 Share Options | Vesting Dates Three | Grant Date Sep 14, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2020    
2017 Share Options | Vesting Dates Three | Grant Date Sep 14, 2017 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2020    
2017 Share Options | Vesting Dates Three | Grant Date Sep 14, 2017 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2020    
2017 Share Options | Vesting Dates Three | Grant Date Sep 15, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 15, 2020    
2017 Share Options | Vesting Dates Three | Grant Date Sep 27, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Mar. 20, 2020    
2017 Share Options | Vesting Dates Three | Grant Date Sep 27, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 27, 2020    
2017 Share Options | Vesting Dates Four | Grant Date May 16, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Oct. 28, 2020    
2017 Share Options | Vesting Dates Four | Grant Date Sep 13, 2017      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 13, 2021    
2017 Share Options | Vesting Dates Four | Grant Date Sep 14, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Mar. 06, 2012    
2017 Share Options | Vesting Dates Four | Grant Date Sep 14, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2021    
2017 Share Options | Vesting Dates Four | Grant Date Sep 14, 2017 Three      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2021    
2017 Share Options | Vesting Dates Four | Grant Date Sep 14, 2017 Four      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 14, 2021    
2017 Share Options | Vesting Dates Four | Grant Date Sep 15, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 15, 2021    
2017 Share Options | Vesting Dates Four | Grant Date Sep 27, 2017 One      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Mar. 20, 2021    
2017 Share Options | Vesting Dates Four | Grant Date Sep 27, 2017 Two      
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]      
Vesting dates Sep. 27, 2021