Losses and Loss Adjustment Expenses - Schedule of Incurred and Paid Claims Development (Detail) $ in Thousands	Dec. 31, 2018 USD ($) Accounts	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Homeowners Multi-peril and Dwelling Fire Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 593,396
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	513,176
All outstanding liabilities before 2012, net of reinsurance	547
Liabilities for losses and loss adjustment, net of reinsurance	80,767
Homeowners Wind-only Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	4,423
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,989
Liabilities for losses and loss adjustment, net of reinsurance	1,434
Losses Specific to Any Hurricane Event prior to 2018 [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	80,313
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	70,845
Liabilities for losses and loss adjustment, net of reinsurance	9,468
Losses Specific to Hurricane Michael in 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	16,520
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	13,376
Liabilities for losses and loss adjustment, net of reinsurance	3,144
Accident Year 2012 [Member] | Homeowners Multi-peril and Dwelling Fire Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	67,220	$ 66,465	$ 67,058	$ 66,505	$ 64,083	$ 62,742	$ 66,425
Total of IBNR Plus Expected Development on Reported Claims	$ 30
Cumulative Number of Reported Claims | Accounts	6,618
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 67,059	65,903	64,667	62,836	59,041	53,225	$ 36,914
Accident Year 2013 [Member] | Homeowners Multi-peril and Dwelling Fire Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	73,763	71,604	72,015	69,906	69,932	67,579
Total of IBNR Plus Expected Development on Reported Claims	$ 546
Cumulative Number of Reported Claims | Accounts	7,008
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 72,492	70,224	68,106	64,257	57,374	$ 40,240
Accident Year 2014 [Member] | Homeowners Multi-peril and Dwelling Fire Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	90,084	88,053	84,917	81,773	75,810
Total of IBNR Plus Expected Development on Reported Claims	$ 2,068
Cumulative Number of Reported Claims | Accounts	7,657
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 87,125	82,463	77,712	68,897	$ 47,650
Accident Year 2015 [Member] | Homeowners Multi-peril and Dwelling Fire Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	101,272	96,173	90,902	78,017
Total of IBNR Plus Expected Development on Reported Claims	$ 3,554
Cumulative Number of Reported Claims | Accounts	7,649
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 95,179	87,784	76,042	50,939
Accident Year 2015 [Member] | Homeowners Wind-only Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	692	569	401	308
Total of IBNR Plus Expected Development on Reported Claims	$ 110
Cumulative Number of Reported Claims | Accounts	100
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 582	465	332	$ 156
Accident Year 2016 [Member] | Homeowners Multi-peril and Dwelling Fire Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	92,684	90,879	81,446
Total of IBNR Plus Expected Development on Reported Claims	$ 6,610
Cumulative Number of Reported Claims | Accounts	6,907
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 83,311	73,037	51,663
Accident Year 2016 [Member] | Homeowners Wind-only Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,814	1,314	1,005
Total of IBNR Plus Expected Development on Reported Claims	$ 220
Cumulative Number of Reported Claims | Accounts	228
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 1,405	1,155	689
Accident Year 2016 [Member] | Losses Specific to Any Hurricane Event prior to 2018 [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	26,211	24,126	21,414
Total of IBNR Plus Expected Development on Reported Claims	$ 2,005
Cumulative Number of Reported Claims | Accounts	2,415
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 23,316	20,025	$ 12,227
Accident Year 2017 [Member] | Homeowners Multi-peril and Dwelling Fire Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	88,937	91,443
Total of IBNR Plus Expected Development on Reported Claims	$ 17,530
Cumulative Number of Reported Claims | Accounts	5,701
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 66,996	43,039
Accident Year 2017 [Member] | Homeowners Wind-only Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,119	1,529
Total of IBNR Plus Expected Development on Reported Claims	$ 330
Cumulative Number of Reported Claims | Accounts	153
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 786	484
Accident Year 2017 [Member] | Losses Specific to Any Hurricane Event prior to 2018 [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	54,080	53,602
Total of IBNR Plus Expected Development on Reported Claims	$ 6,508
Cumulative Number of Reported Claims | Accounts	19,907
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 47,514	$ 43,905
Accident Year 2018 [Member] | Homeowners Multi-peril and Dwelling Fire Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	79,436
Total of IBNR Plus Expected Development on Reported Claims	$ 32,068
Cumulative Number of Reported Claims | Accounts	4,188
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 41,014
Accident Year 2018 [Member] | Homeowners Wind-only Insurance [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	798
Total of IBNR Plus Expected Development on Reported Claims	$ 439
Cumulative Number of Reported Claims | Accounts	108
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 216
Accident Year 2018 [Member] | Losses Specific to Any Hurricane Event prior to 2018 [Member]
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 22
Cumulative Number of Reported Claims | Accounts	952
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 15
Accident Year 2018 [Member] | Losses Specific to Hurricane Michael in 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	16,520
Total of IBNR Plus Expected Development on Reported Claims	$ 2,035
Cumulative Number of Reported Claims | Accounts	611
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 13,376