Net (Loss) Income Per Common Share - Net (Loss) Income Per Common Share on Basic and Diluted Basis (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earnings Per Share [Abstract]
Net income (loss)	$ (175.2)	$ 6.7	$ (54.1)
Dividends on preferred shares	10.5	10.5	4.6
Net income (loss) attributable to common shareholders, diluted	(185.7)	(3.8)	(58.7)
Net income (loss) attributable to common shareholders, basic	$ (185.7)	$ (3.8)	$ (58.7)
Weighted average common shares outstanding - basic (in shares)	34,980,608	34,816,160	34,614,813
Effect of dilutive securities:
Equity compensation awards (in shares)	0	0	0
Weighted average common shares outstanding - diluted (in shares)	34,980,608	34,816,160	34,614,813
Net income (loss) per common share:
Basic (in dollars per share)	$ (5.31)	$ (0.11)	$ (1.70)
Diluted (in dollars per share)	$ (5.31)	$ (0.11)	$ (1.70)