Summary of Restricted Stock Awards Since Inception (Parenthetical) (Detail) (Key Employees, Restricted Stock)	12 Months Ended
Dec. 31, 2003
Key Employees \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share base compensation shares purchased by key employees	122,603

Share Based Compensation Arrangement By Share Based Payment Award Shares Purchased By Employees

No definition available.

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Namespace Prefix:	gbli_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration