OFF-BALANCE SHEET ARRANGEMENTS (Detail) (USD $) In Millions, unless otherwise specified	Dec. 05, 2006
Contingent put option created pursuant to Securities issuance agreement and reinsurance agreement	$ 350.0

Contingent put option created pursuant to Securities issuance agreement entered by company and certain operating subsidiaries and reinsurance agreement entered by certain foreign insurance and reinsurance subsidiaries.

No definition available.

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Namespace Prefix:	xlgroup_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant