UK's R&D Tax Relief Scheme (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2019
Foreign Tax Authority | U.K. tax legislation
Operating Loss Carryforwards [Line Items]
Window to seek relief under U.K. tax legislature	2 years
Tax year 2017
Operating Loss Carryforwards [Line Items]
Claim for refundable cash credit			$ 9.9
Tax year 2018
Operating Loss Carryforwards [Line Items]
Claim for refundable cash credit			$ 9.8
2017 and 2018 tax year claims
Operating Loss Carryforwards [Line Items]
Other income	$ 19.7
2015 and 2016 tax year claims
Operating Loss Carryforwards [Line Items]
Other income		$ 10.1