Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 215.5	$ 265.3	$ 1,249.1
Adjustments to reconcile net income to cash provided by operating activities:
Provision for policy losses and other claims	336.3	486.3	588.7
Depreciation and amortization	188.5	167.5	158.4
Amortization of premiums and accretion of discounts on debt securities, net	8.6	18.8	46.7
Net investment losses (gains)	206.4	515.8	(435.6)
Share-based compensation	49.1	67.3	53.6
Equity in earnings of affiliates, net	(5.4)	(11.0)	(6.9)
Dividends from equity method investments	6.5	11.2	12.2
Changes in assets and liabilities excluding effects of acquisitions and noncash transactions:
Claims paid, including assets acquired, net of recoveries	(381.8)	(434.3)	(482.3)
Net change in income tax accounts	(60.8)	(130.0)	53.0
(Increase) decrease in accounts and accrued income receivable	(159.1)	82.7	(48.2)
(Decrease) increase in accounts payable and accrued liabilities	(51.9)	(265.9)	115.0
Decrease in deferred revenue	(0.1)	(27.9)	(47.1)
Other, net	2.5	31.8	(36.7)
Cash provided by operating activities	354.3	777.6	1,219.9
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions/dispositions, net of cash acquired/divested	(24.7)	(277.5)	(186.8)
Net decrease (increase) in deposits with banks	7.9	(7.7)	(15.0)
Purchases of debt securities	(1,287.8)	(2,980.0)	(6,138.2)
Proceeds from sales of debt securities	1,676.9	1,753.3	1,070.7
Proceeds from maturities of debt securities	812.3	1,171.0	1,864.0
Purchases of equity securities	(170.7)	(157.1)	(198.4)
Proceeds from sales of equity securities	71.0	241.4	171.8
Net change in other investments	(11.6)	(6.8)	(11.7)
Advances under secured financing agreements	(13,309.9)	(15,657.8)	(25,926.2)
Collections of secured financings receivable	13,097.2	15,778.2	26,109.4
Capital expenditures	(263.4)	(259.8)	(160.5)
Proceeds from sales of property and equipment	0.1	6.8	17.8
Proceeds from insurance settlement	2.2	3.0	10.0
Cash provided by (used for) investing activities	599.5	(393.0)	(3,393.1)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net change in deposits	1,788.3	451.1	1,791.7
Borrowings under secured financing agreements	13,383.7	15,532.6	24,602.1
Repayments of secured financings payable	(13,196.7)	(15,695.3)	(24,593.0)
Net proceeds from issuance of unsecured senior notes	0.0	0.0	641.9
Repayment of senior unsecured notes	(250.0)
Repayments of other notes and contracts payable	(6.2)	(6.9)	(6.4)
Net activity related to noncontrolling interests	(7.1)	(2.2)	(4.3)
Net proceeds in connection with share-based compensation	0.4	2.5	6.3
Repurchases of Company shares	(72.7)	(440.7)	(99.2)
Payments of cash dividends	(216.6)	(217.5)	(213.0)
Cash provided by (used for) financing activities	1,423.1	(376.4)	2,126.1
Effect of exchange rate changes on cash	4.9	(12.7)	(0.4)
Net increase (decrease) in cash and cash equivalents	2,381.8	(4.5)	(47.5)
Cash and cash equivalents—Beginning of year	1,223.5	1,228.0	1,275.5
Cash and cash equivalents—End of year	3,605.3	1,223.5	1,228.0
SUPPLEMENTAL INFORMATION:
Interest	124.2	86.5	63.5
Premium taxes	84.2	112.6	86.1
Income taxes	$ 121.0	$ 191.1	$ 339.7