Shareholders' Equity - Schedule of Ordinary Share Capital (Details) $ in Millions	Dec. 31, 2020 USD ($) shares	Dec. 31, 2020 £ / shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2019 £ / shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares) | shares	761,875,338,444		761,875,338,444
Ordinary shares, value, authorized | $	$ 185.6		$ 185.6
Common stock, shares issued (in shares) | shares	761,864,338,444		761,864,338,444
Ordinary shares, value, issued | $	$ 176.5		$ 176.5
Ordinary shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares) | shares	40,000,000		40,000,000
Ordinary shares, value, authorized | $	$ 35.7		$ 35.7
Common stock, shares issued (in shares) | shares	29,000,000		29,000,000
Ordinary shares, value, issued | $	$ 26.6		$ 26.6
Common stock, par value (in GBP per share) | £ / shares		£ 0.50		£ 0.50
Deferred shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares) | shares	761,835,338,444		761,835,338,444
Ordinary shares, value, authorized | $	$ 149.9		$ 149.9
Common stock, shares issued (in shares) | shares	761,835,338,444		761,835,338,444
Ordinary shares, value, issued | $	$ 149.9		$ 149.9
Common stock, par value (in GBP per share) | £ / shares		£ 0.0001		£ 0.0001