Liabilities Assumed on Acquisition (Detail) - Global Indemnity Group Inc - American Reliable Insurance Company $ in Thousands	Jan. 01, 2015 USD ($)
Cash Flow Supplemental Disclosures [Line Items]
Fair value of assets acquired (including goodwill)	$ 383,668
Liabilities assumed	$ 283,871

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities and Noncontrolling Interest

No definition available.

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