Reinsurance Ceded	3 Months Ended
Mar. 31, 2018
Reinsurance Ceded	4. Reinsurance Ceded Alleghany’s reinsurance and insurance subsidiaries reinsure portions of the risks they underwrite in order to reduce the effect of individual or aggregate exposure to losses, manage capacity, protect capital resources, reduce volatility in specific lines of business, improve risk-adjusted portfolio returns and enable them to increase gross premium writings and risk capacity without requiring additional capital. Alleghany’s reinsurance and insurance subsidiaries purchase reinsurance and retrocessional coverages from highly-rated third-party reinsurers. If the assuming reinsurers are unable or unwilling to meet the obligations assumed under the applicable reinsurance agreements, Alleghany’s reinsurance and insurance subsidiaries would remain liable for such reinsurance portion not paid by these reinsurers. As such, funds, trust agreements and letters of credit are held to collateralize a portion of Alleghany’s reinsurance recoverables and Alleghany’s reinsurance and insurance subsidiaries reinsure portions of the risks they underwrite or assume with multiple reinsurance programs. TransRe enters into retrocession arrangements, including property catastrophe retrocession arrangements, in order to reduce the effect of individual or aggregate exposure to losses, reduce volatility in specific lines of business, improve risk-adjusted portfolio returns and increase gross premium writings and risk capacity without requiring additional capital. RSUI reinsures its property lines of business through a program consisting of surplus share treaties, facultative placements, per risk and catastrophe excess of loss treaties. RSUI’s catastrophe reinsurance program and property per risk reinsurance program run on an annual basis from May 1 to the following April 30 and portions expired on April 30, 2018. Both programs were renewed on May 1, 2018 with substantially similar terms as the expired programs.

4. Reinsurance Ceded

Alleghany’s reinsurance and insurance subsidiaries reinsure portions of the risks they underwrite in order to reduce the effect of individual or aggregate exposure to losses, manage capacity, protect capital resources, reduce volatility in specific lines of business, improve risk-adjusted portfolio returns and enable them to increase gross premium writings and risk capacity without requiring additional capital. Alleghany’s reinsurance and insurance subsidiaries purchase reinsurance and retrocessional coverages from highly-rated third-party reinsurers. If the assuming reinsurers are unable or unwilling to meet the obligations assumed under the applicable reinsurance agreements, Alleghany’s reinsurance and insurance subsidiaries would remain liable for such reinsurance portion not paid by these reinsurers. As such, funds, trust agreements and letters of credit are held to collateralize a portion of Alleghany’s reinsurance recoverables and Alleghany’s reinsurance and insurance subsidiaries reinsure portions of the risks they underwrite or assume with multiple reinsurance programs.

TransRe enters into retrocession arrangements, including property catastrophe retrocession arrangements, in order to reduce the effect of individual or aggregate exposure to losses, reduce volatility in specific lines of business, improve risk-adjusted portfolio returns and increase gross premium writings and risk capacity without requiring additional capital.

RSUI reinsures its property lines of business through a program consisting of surplus share treaties, facultative placements, per risk and catastrophe excess of loss treaties. RSUI’s catastrophe reinsurance program and property per risk reinsurance program run on an annual basis from May 1 to the following April 30 and portions expired on April 30, 2018. Both programs were renewed on May 1, 2018 with substantially similar terms as the expired programs.