Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 116,869	$ 60,239	$ 392,055	$ 222,636
Other comprehensive income:
Foreign currency translation adjustment	62	(4,104)	(550)	(8,147)
Income tax effect	(13)	862	115	1,707
Total foreign currency translation adjustment, net of tax	49	(3,242)	(435)	(6,440)
Gross unrealized gain on investments before reclassifications	17,347	33,294	173,235	190,266
Income tax effect	(3,644)	(6,991)	(36,380)	(39,955)
Total change in net unrealized gain on investments, net of tax	13,703	26,303	136,855	150,311
Reclassification adjustments for investments gain or loss to net income:
Net realized gain on investments	(19,393)	(1,886)	(21,350)	(1,835)
Income tax effect	4,073	396	4,484	385
Total gain on investments reclassifications to net income, net of tax	(15,320)	(1,490)	(16,866)	(1,450)
Other comprehensive income (loss) before income tax effect	(1,984)	27,304	151,335	180,284
Income tax effect	416	(5,733)	(31,781)	(37,863)
Other comprehensive income (loss), net of tax	(1,568)	21,571	119,554	142,421
Comprehensive income	115,301	81,810	511,609	365,057
Comprehensive income (loss) attributable to noncontrolling interest	2,757	9,821	(13,902)	8,248
Comprehensive income attributable to NGHC	$ 118,058	$ 91,631	$ 497,707	$ 373,305