Shareholders' Equity - Share Repurchase and Dividends (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	Feb. 22, 2016	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Oct. 30, 2020	May 31, 2019
Shareholders' Equity
Remaining authorization amount for repurchase of common stock						$ 97.7
Dividend declared per common share (in dollars per share)	$ 0.04
Target dividend per annum (in dollars per share)				$ 0.16
May 2019 Repurchase Program
Shareholders' Equity
Amount approved for repurchase of common stock							$ 300.0
Common stock repurchased during the period (in shares)		127,278	1,022,469	1,341,560	3,323,104
Aggregate cost of common stock repurchased during the period		$ 5.0	$ 42.3	$ 55.0	$ 142.3