Shareholders' Equity - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock options, Shares Subject to Options
Outstanding at the end of the period (in shares)	821,464
Stock options
Stock options, Shares Subject to Options
Outstanding at the beginning of the period (in shares)	1,856,176
Granted (in shares)	79,632
Exercised (in shares)	(580,656)
Forfeited /Expired (in shares)	0
Outstanding at the end of the period (in shares)	1,355,152	1,856,176
Exercisable at the end of the period (in shares)	1,093,488
Exercisable and expected to vest at the end of the period (in shares)	1,326,095
Stock options, Weighted Average Option Price
Outstanding at the beginning of the period (in dollars per share)	$ 25.32
Granted (in dollars per share)	85.10
Exercised (in dollars per share)	20.31
Forfeited (in dollars per share)	0
Outstanding at the end of the period (in dollars per share)	30.98	$ 25.32
Exercisable at the end of the period (in dollars per share)	24.96
Exercisable and expected to vest at the end of the period (in dollars per share)	$ 30.32
Stock options, additional information
Weighted Average Remaining Contractual Term, Outstanding	4 years 1 month 6 days	4 years 2 months 12 days
Weighted Average Remaining Contractual Term, Exercisable	3 years 7 months 6 days
Weighted Average Remaining Contractual Term, Exercisable and expected to vest	4 years
Aggregate Intrinsic Value, Outstanding	$ 71.9	$ 53.5
Aggregate Intrinsic Value, Exercisable	64.5
Aggregate Intrinsic Value, Exercisable and expected to vest	71.2
Intrinsic value of options exercised	$ 35.7	$ 6.1	$ 15.2