Investments - Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net Investment Income
Investment income	$ 30,133	$ 34,833	$ 93,975	$ 105,610
Investment expenses	(1,229)	(1,093)	(3,653)	(3,294)
Net investment income	28,904	33,740	90,322	102,316
Reciprocal Exchanges
Net Investment Income
Net investment income	2,254	2,160	6,449	6,454
NGHC, excluding Reciprocal Exchanges
Net Investment Income
Net investment income	26,650	31,580	83,873	95,862
Cash and short-term investments
Net Investment Income
Investment Income	110	1,123	418	3,467
Debt securities, available-for-sale
Net Investment Income
Investment Income	29,526	31,439	92,119	91,631
Other, net
Net Investment Income
Investment Income, Net	497	2,271	1,438	10,512
Other, net \| Related Parties
Net Investment Income
Investment Income, Net	$ (1,425)	$ (10)	$ (2,908)	$ 2,163

Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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