Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues
Premiums	$ 1,272.9	$ 1,181.2	$ 2,536.5	$ 2,362.5
Net investment income	78.7	72.3	161.6	143.4
Net realized and unrealized investment gains (losses):
Net realized gains (losses) from sales and other	(0.4)	7.7	(0.1)	11.0
Net change in fair value of equity securities	6.0		(17.0)
Net other–than–temporary impairment losses on investments recognized in earnings	(1.9)	(1.8)	(2.6)	(3.2)
Total net realized and unrealized investment gains (losses)	3.7	5.9	(19.7)	7.8
Fees and other income	7.5	6.7	15.3	13.3
Total revenues	1,362.8	1,266.1	2,693.7	2,527.0
Losses and expenses
Losses and loss adjustment expenses	783.6	725.0	1,569.4	1,491.5
Amortization of deferred acquisition costs	288.9	264.6	576.9	531.0
Interest expense	11.6	12.2	24.0	24.2
Other operating expenses	158.8	153.3	322.9	310.3
Total losses and expenses	1,242.9	1,155.1	2,493.2	2,357.0
Income before income taxes	119.9	111.0	200.5	170.0
Income tax expense (benefit):
Current	17.3	4.9	37.5	38.8
Deferred	3.4	27.7	(4.0)	7.6
Total income tax expense	20.7	32.6	33.5	46.4
Income from continuing operations	99.2	78.4	167.0	123.6
Net gain from discontinued operations (net of tax benefit of $0.1 for the six months ended June 30, 2018)	0.1
Net income	$ 99.3	$ 78.4	$ 167.0	$ 123.6
Basic:
Income from continuing operations	$ 2.33	$ 1.85	$ 3.93	$ 2.91
Net gain from discontinued operations	0.01
Net income per share	$ 2.34	$ 1.85	$ 3.93	$ 2.91
Weighted average shares outstanding	42.5	42.5	42.5	42.5
Diluted:
Income from continuing operations	$ 2.30	$ 1.83	$ 3.88	$ 2.88
Net gain from discontinued operations	0.01
Net income per share	$ 2.31	$ 1.83	$ 3.88	$ 2.88
Weighted average shares outstanding	43.1	42.8	43.1	42.9