Notes Payable and Debt and Financing Arrangements - Narrative (Details) (Details)	3 Months Ended
Mar. 31, 2013
Debt Instrument [Line Items]
Percentage Ownership Of XLIT Ltd.	100.00%

The Company's percentage ownership in the subsidiaries that had debt outstanding at the balance sheet date.

No definition available.

Name:	xlgroup_PercentageOwnershipOfSubsidiaries
Namespace Prefix:	xlgroup_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration