Condensed Consolidated Statements of Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Premiums and other revenue:
Earned premiums	$ 446.9	$ 389.3	$ 1,279.3	$ 1,167.8
Net investment income	34.5	30.9	103.7	105.0
Fee and other income	3.3	13.0	7.2	20.4
Net realized investment gains (losses):
Net realized investment gains	9.7	6.0	31.1	25.1
Change in fair value of equity securities	4.5	0.0	(22.1)	0.0
Net realized investment gains	14.2	6.0	9.0	25.1
Total revenue	498.9	439.2	1,399.2	1,318.3
Expenses:
Losses and loss adjustment expenses	277.5	326.4	760.2	779.5
Underwriting, acquisition and insurance expenses	168.0	166.1	485.0	474.4
Interest expense	7.9	7.5	23.4	20.4
Fee and other expense	1.9	5.0	5.5	12.4
Foreign currency exchange (gains) losses	(1.7)	0.1	(2.3)	4.0
Total expenses	453.6	505.1	1,271.8	1,290.7
Income (loss) before income taxes	45.3	(65.9)	127.4	27.6
Income tax provision (benefit)	4.7	(4.6)	20.2	6.2
Net income (loss)	$ 40.6	$ (61.3)	$ 107.2	$ 21.4
Net income (loss) per common share:
Basic (in dollars per share)	$ 1.20	$ (1.78)	$ 3.16	$ 0.62
Diluted (in dollars per share)	1.17	(1.78)	3.09	0.60
Dividend declared per common share (in dollars per share)	$ 0.27	$ 0.23	$ 0.81	$ 0.70
Weighted average common shares:
Basic (in shares)	33,956,695	34,475,452	33,921,632	34,586,931
Diluted (in shares)	34,656,328	34,475,452	34,688,843	35,527,173
Net realized investment gains before other-than-temporary impairment losses	$ 14.2	$ 6.2	$ 10.9	$ 26.8
Other-than-temporary impairment losses recognized in earnings:
Other-than-temporary impairment losses on fixed maturities	0.0	(0.1)	(1.9)	(0.1)
Other-than-temporary impairment losses on equity securities	0.0	(0.1)	0.0	(1.6)
Impairment losses recognized in earnings	0.0	(0.2)	(1.9)	(1.7)
Net realized investment gains	$ 14.2	$ 6.0	$ 9.0	$ 25.1