Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 100,573	$ 85,339
Other comprehensive income:
Foreign currency translation adjustment	(342)	(4,253)
Income tax effect	72	889
Total foreign currency translation adjustment, net of tax	(270)	(3,364)
Gross unrealized gain (loss) on investments before reclassifications	(43,400)	76,785
Income tax effect	9,114	(16,125)
Total change in net unrealized gain (loss) on investments, net of tax	(34,286)	60,660
Reclassification adjustments for investments gain or loss to net income:
Net realized loss on investments	2,663	120
Income tax effect	(559)	(25)
Total loss on investments reclassifications to net income, net of tax	2,104	95
Other comprehensive income (loss) before income tax effect	(41,079)	72,652
Income tax effect	8,627	(15,261)
Other comprehensive income (loss), net of tax	(32,452)	57,391
Comprehensive income	68,121	142,730
Comprehensive loss attributable to noncontrolling interest	1,935	1,739
Comprehensive income attributable to NGHC	$ 70,056	$ 144,469