Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 174,613	$ 77,058	$ 275,186	$ 162,397
Other comprehensive income:
Foreign currency translation adjustment	(270)	210	(612)	(4,043)
Income tax effect	56	(44)	128	845
Total foreign currency translation adjustment, net of tax	(214)	166	(484)	(3,198)
Gross unrealized gain on investments before reclassifications	196,361	80,187	155,888	156,972
Income tax effect	(41,236)	(16,839)	(32,736)	(32,964)
Total change in net unrealized gain on investments, net of tax	155,125	63,348	123,152	124,008
Reclassification adjustments for investments gain or loss to net income:
Net realized (gain) loss on investments	(1,693)	(69)	(1,957)	51
Income tax effect	356	14	411	(11)
Total (gain) loss on investments reclassifications to net income, net of tax	(1,337)	(55)	(1,546)	40
Other comprehensive income before income tax effect	194,398	80,328	153,319	152,980
Income tax effect	(40,824)	(16,869)	(32,197)	(32,130)
Other comprehensive income, net of tax	153,574	63,459	121,122	120,850
Comprehensive income	328,187	140,517	396,308	283,247
Comprehensive income attributable to noncontrolling interest	(18,594)	(3,312)	(16,659)	(1,573)
Comprehensive income attributable to NGHC	$ 309,593	$ 137,205	$ 379,649	$ 281,674