Condensed Financial Information of HCI Group, Inc. - Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Net investment income													$ 16,581	$ 11,439	$ 9,087
Net realized investment gains													6,183	4,346	2,601
Net unrealized investment (losses) gains													(10,202)	92
Other-than-temporary impairment loss charged to investment income													(80)	(1,467)	(2,482)
Gain on repurchases of convertible senior notes															153
Loss on repurchases of senior notes														(743)
Interest expense	$ (4,569)	$ (4,552)	$ (4,505)	$ (4,470)	$ (4,439)	$ (4,408)	$ (4,378)	$ (3,542)	$ (2,967)	$ (2,672)	$ (2,611)	$ (2,829)	(18,096)	(16,767)	(11,079)
Income tax benefit													(9,177)	8,731	(17,835)
Net (loss) income	$ (8,466)	$ 8,997	$ 6,403	$ 10,791	$ 12,091	$ (40,546)	$ 9,542	$ 12,020	$ 4,608	$ 11,333	$ 7,024	$ 6,056	17,725	(6,893)	29,021
HCI Group [Member]
Condensed Financial Statements, Captions [Line Items]
Net investment income													5,348	2,799	1,204
Net realized investment gains													1,544	367	151
Net unrealized investment (losses) gains													(1,514)	92
Other-than-temporary impairment loss charged to investment income													(80)	(209)	(15)
Gain on repurchases of convertible senior notes															153
Loss on repurchases of senior notes														(743)
Interest expense													(17,007)	(15,704)	(10,346)
Operating expenses													(5,429)	(5,489)	(5,158)
Loss before income tax benefit and equity in income of subsidiaries													(17,138)	(18,887)	(14,011)
Income tax benefit													1,856	9,605	4,878
Net loss before equity in income of subsidiaries													(15,282)	(9,282)	(9,133)
Equity in income of subsidiaries													33,007	2,389	38,154
Net (loss) income													$ 17,725	$ (6,893)	$ 29,021