Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 558.6	$ 1,056.4	$ 370.5
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred policy acquisition costs	(2.5)	(8.9)	(18.4)
Premiums and other receivables	(123.4)	32.5	(29.3)
Unpaid claims and related items	340.7	214.6	148.4
Unearned premiums and other policyholders' liabilities	34.6	32.2	95.1
Income taxes	(18.3)	37.2	(69.5)
Prepaid federal income taxes	0.0	129.8	(15.5)
Reinsurance balances and funds	77.0	(9.7)	13.5
Realized Investment Gains (Losses)	(14.2)	(36.6)	(58.2)
Unrealized from changes in fair value of equity securities	156.2	(599.5)	293.8
Accounts payable, accrued expenses and other	176.2	88.0	30.0
Total	1,185.0	936.2	760.5
Fixed maturity securities:
Maturities and early calls	1,280.1	779.0	964.0
Sales	399.5	663.1	299.1
Sales of:
Equity securities	162.3	809.9	402.6
Other - net	8.8	33.0	19.4
Purchases of:
Fixed maturity securities:	(2,059.3)	(1,702.1)	(1,421.9)
Equity securities	(321.0)	(815.6)	(752.5)
Other - net	(50.2)	(60.9)	(51.6)
Purchase of a business	0.0	(1.2)	(13.1)
Net decrease (increase) in short-term investments	(265.0)	(129.7)	314.2
Other - net	(0.3)	0.0	0.1
Total	(845.2)	(424.6)	(239.5)
Cash flows from financing activities:
Issuance of common shares	6.7	13.8	13.1
Redemption of debentures and notes	(8.6)	(8.4)	(4.7)
Origination of Loans to Employee Stock Ownership Plans	(50.0)	0.0	(50.0)
Dividends on common shares (including a special dividend paid in September 2019 of $303.4 and a special dividend declared in December 2017 and paid in January 2018 of $269.2)	(250.1)	(538.7)	(498.8)
Other - net	2.0	0.2	(6.0)
Total	(300.0)	(533.1)	(546.5)
Increase (decrease) in cash:	39.8	(21.4)	(25.6)
Cash, beginning of year	78.8	100.3	125.9
Cash, end of year	118.7	78.8	100.3
Supplemental cash flow information:
Cash paid (received) during the period for: Interest	41.4	42.1	50.8
Cash paid (received) during the period for: Income taxes	$ 149.3	$ 229.4	$ 137.2