Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2022

Stockholders' Equity Note [Abstract]

Schedule of Common Stock Repurchases

The following table presents the shares of Common Stock that Alleghany repurchased in the three months ended March 31, 2022 and 2021:

	Three Months Ended March 31,
	2022		2021
Shares repurchased		144,864		103,025
Cost of shares repurchased (in millions)	$	96.0	$	63.2
Average price per share repurchased	$	662.60	$	613.36

Reconciliation of Accumulated Other Comprehensive Income (Loss)

The following tables present a reconciliation of the changes during the three months ended March 31, 2022 and 2021 in accumulated other comprehensive income (loss) attributable to Alleghany stockholders:

	Unrealized Appreciation of Investments			Unrealized Currency Translation Adjustment			Retirement Plans			Total
	($ in millions)
Balance as of January 1, 2022	$	259.1		$	(103.7	)	$	(13.6	)	$	141.8
Other comprehensive (loss) income, net of tax:
Other comprehensive (loss) income before reclassifications		(614.3	)		(0.5	)		0.1			(614.7	)
Reclassifications from accumulated other comprehensive income		8.4			—			—			8.4
Total		(605.9	)		(0.5	)		0.1			(606.3	)
Balance as of March 31, 2022	$	(346.8	)	$	(104.2	)	$	(13.5	)	$	(464.5	)

	Unrealized Appreciation of Investments			Unrealized Currency Translation Adjustment			Retirement Plans			Total
	($ in millions)
Balance as of January 1, 2021	$	564.9		$	(99.4	)	$	(13.1	)	$	452.4
Other comprehensive income (loss), net of tax:
Other comprehensive (loss) income before reclassifications		(217.9	)		2.5			(1.0	)		(216.4	)
Reclassifications from accumulated other comprehensive income		(11.8	)		—			—			(11.8	)
Total		(229.7	)		2.5			(1.0	)		(228.2	)
Balance as of March 31, 2021	$	335.2		$	(96.9	)	$	(14.1	)	$	224.2

Reclassifications of Accumulated Other Comprehensive Income (Loss)

The following table presents unrealized appreciation of investment reclassifications out of accumulated other comprehensive income or loss attributable to Alleghany stockholders during the three months ended March 31, 2022 and 2021:

Accumulated Other		Three Months Ended March 31,
Comprehensive Income Component	Line in Consolidated Statement of Earnings	2022			2021
		($ in millions)
Unrealized appreciation of investments:	Net realized capital gains	$	10.0		$	(12.9	)
	Change in allowance for credit losses on      available for sale securities		0.6			(2.0	)
	Income taxes		(2.2	)		3.1
Total reclassifications:	Net losses (earnings)	$	8.4		$	(11.8	)