Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net income	$ 119.3	$ 119.8	$ 157.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7.4	8.2	9.0
Stock-based compensation	9.1	9.7	10.1
Amortization of cloud computing arrangements	14.2	9.0	5.3
Amortization of premium on investments, net	8.5	9.8	8.7
Allowance for expected credit losses	(0.3)	6.6	(2.1)
Deferred income tax expense	6.7	(13.4)	6.0
Net realized and unrealized gains on investments	(54.6)	(19.0)	(51.1)
Asset impairment charges	1.0	0.8	0.0
Change in operating assets and liabilities:
Premiums receivable	(12.1)	47.4	49.5
Reinsurance recoverable on paid and unpaid losses	20.2	35.1	20.4
Cloud computing arrangements	(7.9)	(25.6)	(12.9)
Operating lease right-of-use-assets	3.2	(2.3)	(15.9)
Current federal income taxes	(7.9)	22.0	(7.4)
Unpaid losses and loss adjustment expenses	(88.2)	(123.4)	(63.4)
Unearned premiums	5.6	(38.0)	0.8
Accounts payable, accrued expenses and other liabilities	(2.5)	(4.0)	(8.1)
Deferred reinsurance gain–LPT Agreement	(11.0)	(11.7)	(12.5)
Contingent commission receivable–LPT Agreement	(0.5)	(0.2)	18.8
Operating lease liabilities	(3.3)	2.1	17.8
Non-cancellable obligations	(2.4)	1.1	4.2
Other	6.3	(1.0)	(11.8)
Net cash provided by operating activities	10.8	33.0	122.5
Investing activities
Purchases of fixed maturity securities	(516.6)	(645.6)	(359.0)
Purchases of equity securities	(199.5)	(179.5)	(240.8)
Purchases of short-term investments	(12.5)	(135.9)	0.0
Purchases of other invested assets	(17.3)	(8.3)	(28.4)
Proceeds from sale of fixed maturity securities	206.7	349.5	163.0
Proceeds from sale of equity securities	135.9	243.4	232.4
Proceeds from maturities and redemptions of fixed maturity securities	373.5	359.2	309.9
Proceeds from maturities of short-term investments	28.3	110.6	25.0
Net change in unsettled investment purchases and sales	3.4	(3.6)	(24.7)
Capital expenditures and other	(3.6)	(5.5)	(12.1)
Payments to Acquire Businesses, Net of Cash Acquired	0.0	0.0	(16.1)
Net cash (used in) provided by investing activities	(1.7)	84.3	49.2
Financing activities
Acquisition of common stock	(42.6)	(99.4)	(67.5)
Cash transactions related to stock-based compensation	(2.7)	(1.8)	(2.5)
Dividends paid to stockholders and eligible equity plan holders	(29.0)	(30.5)	(28.3)
Proceeds from FHLB advances	0.0	35.0	0.0
Repayments of Notes Payable	(20.0)	(15.0)	0.0
Proceeds from Lines of Credit	27.0	0.0	0.0
Repayments on line of credit advances and notes payable	(27.0)	0.0	(20.0)
Payments on finance leases	(0.1)	(0.2)	(0.2)
Net cash used in financing activities	(94.4)	(111.9)	(118.5)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(85.3)	5.4	53.2
Cash, cash equivalents, and restricted cash at the beginning of the period	160.6	155.2	102.0
Cash, cash equivalents, and restricted cash at the end of the period	75.3	160.6	155.2
Non-cash transactions
Financed property and equipment purchases	0.3	0.1	0.7
Conversion of Stock, Amount Converted	20.0	0.0	0.0
Cash, cash equivalents, and restricted cash
Cash and cash equivalents	75.1	160.4
Restricted cash and cash equivalents	0.2	0.2
Total cash, cash equivalents, and restricted cash	$ 75.3	$ 160.6	$ 155.2