Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash Flows From Operating Activities
Net income	$ 255.2	$ 194.1
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized and unrealized investment (gains) losses	(73.0)	59.7
Loss from repayment of debt		6.2
Net amortization and depreciation	12.5	13.9
Stock-based compensation expense	16.8	14.4
Amortization of defined benefit plan costs	2.5	4.5
Deferred income tax expense (benefit)	12.4	(27.9)
Change in deferred acquisition costs	(67.1)	(15.1)
Change in premiums receivable, net of reinsurance premiums payable	(144.0)	(78.7)
Change in loss, loss adjustment expense and unearned premium reserves	776.9	412.6
Change in reinsurance recoverable	(128.4)	(27.3)
Change in expenses and taxes payable	(51.0)	(9.0)
Other, net	(17.4)	(0.8)
Net cash provided by operating activities	595.4	546.6
Cash Flows From Investing Activities
Proceeds from disposals and maturities of fixed maturities	1,155.6	961.0
Proceeds from disposals of equity securities and other investments	209.6	153.5
Purchase of fixed maturities	(1,571.5)	(1,423.1)
Purchase of equity securities and other investments	(125.7)	(159.6)
Capital expenditures	(5.7)	(12.1)
Net cash used in investing activities	(337.7)	(480.3)
Cash Flows From Financing Activities
Proceeds from exercise of employee stock options	19.3	4.8
Proceeds from debt borrowings, net		296.4
Dividends paid to shareholders	(75.6)	(74.0)
Repurchases of common stock	(142.6)	(94.3)
Repayment of debt		(175.8)
Other financing activities	(8.2)	(7.6)
Net cash used in financing activities	(207.1)	(50.5)
Net change in cash and cash equivalents	50.6	15.8
Cash and cash equivalents, beginning of period	120.6	215.7
Cash and cash equivalents, end of period	$ 171.2	$ 231.5