Reinsurance

12 Months Ended

Dec. 31, 2019

Supplemental Schedule Of Reinsurance Premiums For Insurance Companies [Abstract]

Reinsurance

Schedule IV – Reinsurance

ALLEGHANY CORPORATION AND SUBSIDIARIES

Year ended December 31,

Year	Line of Business	Gross Amount		Ceded to Other Companies		Assumed from Other Companies		Net Amount		Percentage of Amount Assumed to Net
		($ in millions)
2019	Property and casualty	$	2,114.1	$	904.8	$	4,268.8	$	5,478.1		77.9	%
2018	Property and casualty	$	1,935.3	$	840.5	$	3,881.4	$	4,976.2		78.0	%
2017	Property and casualty	$	1,932.0	$	767.3	$	3,790.3	$	4,955.0		76.5	%