Condensed Consolidated Statements of Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Premiums and other revenue:
Earned premiums	$ 487.5	$ 445.5	$ 1,423.9	$ 1,313.9
Net investment income	46.1	42.0	143.2	79.0
Net realized investment gains (losses):
Net realized investment gains (losses)	0.6	(5.7)	3.3	32.7
Change in fair value of equity securities	(5.1)	10.5	30.7	(13.7)
Credit losses on fixed maturity securities	(0.8)	(10.5)	(1.5)	(43.0)
Net realized investment (losses) gains	(5.3)	(5.7)	32.5	(24.0)
Total revenue	528.3	481.8	1,599.6	1,368.9
Expenses:
Losses and loss adjustment expenses	311.7	328.9	890.9	883.0
Underwriting, acquisition and insurance expenses	177.1	161.9	530.8	489.8
Non-operating expenses	8.2	3.0	20.9	9.8
Interest expense	5.5	6.9	16.3	21.7
Fee and other (income) expense, net	(1.1)	(0.8)	(1.8)	(2.7)
Foreign currency exchange (gains) losses	(1.3)	8.4	4.4	13.6
Total expenses	500.1	508.3	1,461.5	1,415.2
Income (loss) before income taxes	28.2	(26.5)	138.1	(46.3)
Income tax provision (benefit)	5.8	(3.4)	16.1	6.9
Net income (loss)	22.4	(23.1)	122.0	(53.2)
Dividends on preferred shares	2.6	2.0	7.9	2.0
Net Income (Loss) Available to Common Stockholders, Diluted, Total	19.8	(25.1)	114.1	(55.2)
Net Income (Loss) Available to Common Stockholders, Basic, Total	$ 19.8	$ (25.1)	$ 114.1	$ (55.2)
Net income (loss) attributable to common shareholders per common share:
Basic (in dollars per share)	$ 0.57	$ (0.72)	$ 3.28	$ (1.60)
Diluted (in dollars per share)	0.56	(0.72)	3.26	(1.60)
Cash dividend declared - common shares (in dollars per share)	$ 0.31	$ 0.31	$ 0.93	$ 0.93
Weighted average common shares:
Basic (in shares)	34,854,724	34,667,266	34,796,528	34,590,659
Diluted (in shares)	35,036,700	34,667,266	35,062,416	34,590,659