Investments - Summary of Fixed Maturities with Unrealized Losses (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	$ 128,661	$ 78,670
Less Than 12 Months, Unrealized Losses	5,240	658
More Than 12 Months, Fair Value	15,483	100,614
More Than 12 Months, Unrealized Losses	1,348	992
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value		7,461
Less Than 12 Months, Unrealized Losses		46
More Than 12 Months, Fair Value		5,395
More Than 12 Months, Unrealized Losses		42
Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	11,918	23,339
Less Than 12 Months, Unrealized Losses	224	293
More Than 12 Months, Fair Value		2,327
More Than 12 Months, Unrealized Losses		2
Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	111,062	19,363
Less Than 12 Months, Unrealized Losses	4,957	263
More Than 12 Months, Fair Value	11,196	18,803
More Than 12 Months, Unrealized Losses	1,287	250
Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	5,681	28,507
Less Than 12 Months, Unrealized Losses	59	56
More Than 12 Months, Fair Value	4,287	74,089
More Than 12 Months, Unrealized Losses	$ 61	$ 698