Consolidated Balance Sheets - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Assets
Fixed maturities (amortized cost: $44,556.0, $35,082.8, and $35,589.1)		$ 45,045.7	$ 36,810.9	$ 36,313.5
Short-term investments (amortized cost: $1,088.7, $4,667.8, and $5,218.5)		1,088.7	5,218.5	4,667.8
Total available-for-sale securities		46,134.4	42,029.4	40,981.3
Nonredeemable preferred stocks (cost: $1,479.9, $1,302.7, and $1,358.7)		1,572.8	1,447.9	1,323.2
Common equities (cost: $1,238.4, $1,130.0, and $1,187.3)		4,580.2	4,053.0	3,459.8
Total equity securities		6,153.0	5,500.9	4,783.0
Total investments		52,287.4	47,530.3	45,764.3
Cash and cash equivalents		270.6	76.5	90.1
Restricted Cash and Cash Equivalents		14.9	0.0	1.0
Cash and cash equivalents		285.5	76.5	91.1
Accrued investment income		168.6	176.4	181.5
Premiums receivable, net of allowance for credit losses of $257.3, $313.2, and $356.2		10,246.7	8,160.1	8,574.3
Reinsurance recoverables		5,044.9	4,019.4	3,987.3
Prepaid reinsurance premiums		661.1	368.1	463.4
Deferred acquisition costs		1,430.7	1,237.2	1,265.0
Property and equipment, net of accumulated depreciation of $1,422.2, $1,264.5, and $1,291.4		1,161.0	1,106.0	1,181.6
Goodwill		452.7	452.7	452.7
Intangible assets, net of accumulated amortization of $369.2, $312.0, and $326.1		131.9	171.4	185.5
Other assets		747.6	800.2	759.3
Total assets		72,618.1	64,098.3	62,906.0
Liabilities
Unearned premiums		16,671.4	13,437.5	14,199.3
Loss and loss adjustment expense reserves		25,926.3	20,265.8	19,589.2
Net federal deferred income taxes		110.7	310.0	227.9
Dividends payable on common shares		58.5	2,694.5	58.6
Accounts payable, accrued expenses, and other liabilities		6,394.9	4,955.8	5,348.4
Debt	[1]	4,898.2	5,396.1	5,395.4
Total liabilities		54,060.0	47,059.7	44,818.8
Shareholders’ Equity
Serial Preferred Shares, Series B, no par value (cumulative, liquidation preference $1,000 per share) (authorized, issued, and outstanding 0.5)		493.9	493.9	493.9
Common shares, $1.00 par value (authorized 900.0; issued 797.6, 797.5, and 797.5, including treasury shares of 212.6, 211.9, and 212.3)		585.0	585.2	585.6
Paid-in capital		1,735.9	1,672.9	1,629.4
Retained earnings		15,390.0	13,354.9	14,427.7
Accumulated other comprehensive income (loss):
Net unrealized gains (losses) on fixed-maturity securities		369.0	947.3	966.4
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax		(15.0)	(15.6)	(15.8)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax		(0.7)	0.0	0.0
Total accumulated other comprehensive income (loss)		353.3	931.7	950.6
Total shareholders’ equity		18,558.1	17,038.6	18,087.2
Total liabilities and shareholders’ equity		$ 72,618.1	$ 64,098.3	$ 62,906.0

[1] Consists of long-term debt. See Note 4 – Debt for further discussion.