Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net (loss) income	$ (10.7)	$ 21.0	$ 51.2
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization, net	12.5	14.6	15.7
Share-based compensation	4.2	3.7	4.5
Net realized gain on investments	(65.1)	(36.5)	(24.3)
Changes in operating assets and liabilities:
Deferred policy acquisition benefits	12.0	(0.7)	(2.6)
Accrued investment income and other assets	3.5	(4.5)	(2.4)
Postretirement and pension benefits	(9.0)	(28.8)	(6.0)
Reinsurance recoverable on losses and loss expenses payable and prepaid reinsurance premiums	0.2	3.0	3.0
Other liabilities and due to/from affiliates, net	6.0	7.3	(39.9)
Losses and loss expenses payable	74.0	128.6	69.8
Unearned premiums	(6.0)	1.5	3.9
Excess tax expense on share-based awards	0.0	(0.2)	(0.3)
Federal income taxes	46.3	4.5	13.7
Cash provided from December 31, 2014 unearned premium transfer related to the homeowners quota-share reinsurance arrangement	0.0	0.0	63.5
Net cash provided by operating activities	67.9	113.5	149.8
Cash flows from investing activities:
Purchases of fixed maturities available-for-sale	(505.4)	(589.3)	(573.9)
Purchases of equity securities available-for-sale	(185.9)	(143.1)	(154.0)
Purchases of other invested assets	(1.4)	(1.5)	(6.9)
Maturities, calls and pay downs of fixed maturities available-for-sale	233.6	240.9	241.0
Sales of fixed maturities available-for-sale	184.8	211.6	180.7
Sales of equity securities available-for-sale	252.7	153.0	144.8
Sales of other invested assets available-for-sale	1.1	0.8	0.7
Net disposals of property and equipment	0.0	0.0	(0.1)
Net cash used in investing activities	(20.5)	(127.6)	(167.7)
Cash flows from financing activities:
Proceeds from issuance of common stock	10.2	2.2	6.2
Payments to acquire treasury stock	(0.3)	(0.2)	(0.3)
Payments of dividends (affiliates $10.4, $10.4 and $10.4, respectively)	(16.9)	(16.6)	(16.5)
Excess tax expense on share-based awards	0.0	0.2	0.3
Proceeds from long-term debt	0.0	21.5	0.0
Net cash (used in) provided by financing activities	(7.0)	7.1	(10.3)
Net increase (decrease) in cash and cash equivalents	40.4	(7.0)	(28.2)
Cash and cash equivalents at beginning of year	51.1	58.1	86.3
Cash and cash equivalents at end of year	91.5	51.1	58.1
Supplemental disclosures:
Interest paid (affiliates $0.8, $0.8 and $0.7, respectively)	5.7	5.4	5.3
Proceeds from Income Tax Refunds	$ (1.6)
Federal income tax (refund) paid		$ 0.0	$ 6.4