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Share-Based Compensation - Restricted Stock Units Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Fair value of restricted stocks granted	$ 24.1	$ 18.9	$ 5.9
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Fair value of restricted stocks granted	$ 31.8	$ 59.7	$ 37.7
Restricted stocks available for future grant under the Company's option plans (in shares)	3,300,000
Restricted Stock Units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period of restricted stocks	3 years
Restricted Stock Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period of restricted stocks	4 years