Net Income Per Share - Schedule of Calculation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income	$ 28.8	$ 62.0	$ 91.7
Denominator – Weighted-average common shares outstanding (in thousands):
Basic	15,802	15,997	16,585
Add: dilutive effect of non-vested common shares, restricted stock units and performance shares	111	206	289
Diluted	15,913	16,203	16,874
Net income per common share, Basic:	$ 1.82	$ 3.88	$ 5.53
Net income per common share, Diluted:	$ 1.81	$ 3.83	$ 5.43