Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Premiums and other revenue:
Earned premiums	$ 399.1	$ 344.9	$ 778.5	$ 689.8
Net investment income	43.6	35.7	74.1	56.9
Fee and other income	3.8	5.8	7.4	12.6
Net realized investment and other gains (losses)	4.5	(2.1)	19.1	(4.9)
Total revenue	451.0	384.3	879.1	754.4
Expenses:
Losses and loss adjustment expenses	230.6	196.6	453.1	388.2
Underwriting, acquisition and insurance expenses	154.7	133.0	308.3	265.6
Interest expense	7.0	4.9	12.9	9.7
Fee and other expense	3.3	5.7	7.4	12.2
Foreign currency exchange losses	4.6	4.5	3.9	6.0
Total expenses	400.2	344.7	785.6	681.7
Income before income taxes	50.8	39.6	93.5	72.7
Provision for income taxes	4.8	8.7	10.8	14.1
Net income	$ 46.0	$ 30.9	$ 82.7	$ 58.6
Net income per common share:
Basic	$ 1.52	$ 1.03	$ 2.75	$ 1.93
Diluted	1.48	1.00	2.67	1.89
Dividend declared per common share	$ 0.27	$ 0.22	$ 0.54	$ 0.42
Weighted average common shares:
Basic	30,201,457	30,187,592	30,124,696	30,333,417
Diluted	31,048,081	30,810,156	30,995,172	30,971,189
Net realized investment and other gains before other-than-temporary impairment losses	$ 5.6	$ 2.8	$ 20.6	$ 1.7
Other-than-temporary impairment losses recognized in earnings:
Other-than-temporary impairment losses on fixed maturities	0.0	(0.5)	0.0	(1.1)
Other-than-temporary impairment losses on equity securities	(1.1)	(4.4)	(1.5)	(5.5)
Impairment losses recognized in earnings	(1.1)	(4.9)	(1.5)	(6.6)
Net realized investment and other gains (losses)	$ 4.5	$ (2.1)	$ 19.1	$ (4.9)