Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Premiums and other revenue:
Earned premiums	$ 431.7	$ 417.7	$ 852.2	$ 832.4
Net investment income	42.8	33.2	76.7	69.2
Fee and other income	2.1	1.9	4.4	3.9
Net realized investment (losses) gains:
Net realized investment (losses) gains	(0.6)	6.2	(2.3)	21.4
Change in fair value of equity securities	12.6	4.3	66.8	(26.6)
Net realized investment gains (losses)	12.0	10.5	64.5	(5.2)
Total revenue	488.6	463.3	997.8	900.3
Expenses:
Losses and loss adjustment expenses	284.8	245.5	522.7	482.7
Underwriting, acquisition and insurance expenses	168.9	156.8	329.6	317.0
Interest expense	9.3	7.8	17.8	15.5
Fee and other expense	1.3	1.6	2.6	3.6
Foreign currency exchange gains	(5.3)	(5.5)	(4.6)	(0.6)
Total expenses	459.0	406.2	868.1	818.2
Income before income taxes	29.6	57.1	129.7	82.1
Income tax provision	0.8	15.3	9.7	15.5
Net income	$ 28.8	$ 41.8	$ 120.0	$ 66.6
Net income per common share:
Basic (in dollars per share)	$ 0.84	$ 1.23	$ 3.52	$ 1.96
Diluted (in dollars per share)	0.83	1.20	3.45	1.92
Dividend declared per common share (in dollars per share)	$ 0.31	$ 0.27	$ 0.62	$ 0.54
Weighted average common shares:
Basic (in shares)	34,195,250	33,938,509	34,090,372	33,903,809
Diluted (in shares)	34,779,991	34,668,918	34,759,548	34,704,811
Net realized investment gains (losses) before other-than-temporary impairment losses	$ 14.5	$ 11.4	$ 71.3	$ (3.3)
Other-than-temporary impairment losses recognized in earnings:
Other-than-temporary impairment losses on fixed maturities	(2.5)	(0.9)	(6.8)	(1.9)
Impairment losses recognized in earnings	$ (2.5)	$ (0.9)	$ (6.8)	$ (1.9)