Consolidated Balance Sheets - USD ($) $ in Millions		Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Assets
Fixed maturities (amortized cost: $42,378.0, $33,467.9, and $35,589.1)		$ 43,031.0	$ 36,810.9	$ 34,726.4
Short-term investments (amortized cost: $1,710.6, $4,700.5, and $5,218.5)		1,710.6	5,218.5	4,700.5
Total available-for-sale securities		44,741.6	42,029.4	39,426.9
Nonredeemable preferred stocks (cost: $1,536.2, $1,205.4, and $1,358.7)		1,662.3	1,447.9	1,180.6
Common equities (cost: $1,213.4, $1,128.8, and $1,187.3)		4,538.9	4,053.0	3,170.4
Total equity securities		6,201.2	5,500.9	4,351.0
Total investments		50,942.8	47,530.3	43,777.9
Cash and cash equivalents		99.5	76.5	108.0
Restricted Cash and Cash Equivalents		15.1	0.0	1.1
Cash and cash equivalents		114.6	76.5	109.1
Accrued investment income		179.3	176.4	190.8
Premiums receivable, net of allowance for credit losses of $245.2, $437.9, and $356.2		9,436.2	8,160.1	7,557.4
Reinsurance recoverables		4,709.1	4,019.4	3,654.3
Prepaid reinsurance premiums		620.0	368.1	361.3
Deferred acquisition costs		1,360.6	1,237.2	1,154.8
Property and equipment, net of accumulated depreciation of $1,396.5, $1,241.7, and $1,291.4		1,086.4	1,106.0	1,189.8
Goodwill		452.7	452.7	452.7
Intangible assets, net of accumulated amortization of $354.6, $297.8, and $326.1		146.5	171.4	199.7
Other assets		776.1	800.2	773.6
Total assets		69,824.3	64,098.3	59,421.4
Liabilities
Unearned premiums		15,555.9	13,437.5	13,055.6
Loss and loss adjustment expense reserves		23,895.6	20,265.8	18,512.0
Net federal deferred income taxes		219.4	310.0	211.2
Dividends payable on common shares		58.5	2,694.5	58.5
Accounts payable, accrued expenses, and other liabilities		6,021.8	4,955.8	5,518.8
Debt	[1]	5,397.5	5,396.1	5,394.7
Total liabilities		51,148.7	47,059.7	42,750.8
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 212.4, 212.1, and 212.3)		585.2	585.2	585.4
Paid-in capital		1,712.3	1,672.9	1,614.5
Retained earnings		15,401.0	13,354.9	13,001.8
Accumulated other comprehensive income (loss):
Net unrealized gains (losses) on fixed-maturity securities		498.8	947.3	991.0
Net unrealized losses on forecasted transactions		(15.1)	(15.6)	(16.0)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax		(0.5)	0.0	0.0
Total accumulated other comprehensive income (loss)		483.2	931.7	975.0
Total shareholders’ equity		18,675.6	17,038.6	16,670.6
Total liabilities and shareholders’ equity		$ 69,824.3	$ 64,098.3	$ 59,421.4

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