Condensed Financial Information of Registrant (Parent Only) Statement of Operations and Comprehensive Income (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Net investment income		$ 9,659	$ 11,348	$ 13,826	$ 7,219	$ 12,234	$ 11,750	$ 10,954	$ 11,404	$ 42,052	$ 46,342	$ 39,323
Net realized investment gains (losses)		24,052	(2,690)	3,590	10,390	(24,740)	5,319	2,830	(316)	35,342	(16,907)	1,576
Other income (loss)										1,816	1,728	6,582
Total revenues										604,472	498,938	485,515
Expenses:
Interest expense										20,022	19,694	16,906
Income (loss) before income taxes		35,610	6,404	15,849	23,894	(86,602)	436	5,793	4,448	81,757	(75,925)	(10,050)
Equity in net income (loss) of subsidiaries										0	0	0
Net income (loss)		$ 29,031	$ 6,721	$ 14,663	$ 19,600	$ (73,317)	$ 3,728	$ 7,192	$ 5,701	70,015	(56,696)	(9,551)
Other comprehensive income (loss), net of tax:
Unrealized holding gains (losses)										43,980	(20,748)	9,677
Equity in other comprehensive income (loss) of unconsolidated subsidiaries										0	0	0
Reclassification adjustment for (gains) losses included in net income (loss)										5,437	(2,450)	848
Other comprehensive income (loss), net of tax										38,840	(20,186)	9,601
Comprehensive income (loss), net of tax										108,855	(76,882)	50
Parent Company | Global Indemnity Limited
Revenues:
Net investment income										2,295	658	361
Net realized investment gains (losses)										574	(154)	(368)
Other income (loss)										0	0	6
Total revenues										2,869	504	(1)
Expenses:
Intercompany interest expense	[1]									844	7,034	2,477
Interest expense										264	5,960	15,872
Other expenses										6,692	11,317	16,807
Income (loss) before income taxes										(4,931)	(23,807)	(35,157)
Equity in net income (loss) of subsidiaries	[1]									74,946	(32,889)	25,606
Net income (loss)										70,015	(56,696)	(9,551)
Other comprehensive income (loss), net of tax:
Unrealized holding gains (losses)										872	(499)	(216)
Equity in other comprehensive income (loss) of unconsolidated subsidiaries	[1]									38,520	(19,841)	9,449
Reclassification adjustment for (gains) losses included in net income (loss)										(552)	154	368
Other comprehensive income (loss), net of tax										38,840	(20,186)	9,601
Comprehensive income (loss), net of tax										$ 108,855	$ (76,882)	$ 50

[1] This item has been eliminated in the Company’s Consolidated Financial Statements.