Investments - Summary of Securities with Gross Unrealized Loss Positions Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss, Less than Twelve Months	$ (479)	$ (21)
Estimated Fair Value, Less than Twelve Months	10,571	7,234
Gross Unrealized Loss, Total	(479)	(21)
Estimated Fair Value, Total	10,571	7,234
Fixed-Maturity Securities [Member] | Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss, Less than Twelve Months	(392)	(3)
Estimated Fair Value, Less than Twelve Months	7,785	4,597
Gross Unrealized Loss, Twelve Months or Longer		0
Estimated Fair Value, Twelve Months or Longer		0
Gross Unrealized Loss, Total	(392)	(3)
Estimated Fair Value, Total	7,785	4,597
Fixed-Maturity Securities [Member] | State, Municipalities, and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss, Less than Twelve Months	(12)
Estimated Fair Value, Less than Twelve Months	1,270
Gross Unrealized Loss, Total	(12)
Estimated Fair Value, Total	1,270
Fixed-Maturity Securities [Member] | Exchange-Traded Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss, Less than Twelve Months	(74)	(15)
Estimated Fair Value, Less than Twelve Months	1,481	345
Gross Unrealized Loss, Twelve Months or Longer	0	0
Estimated Fair Value, Twelve Months or Longer	0	0
Gross Unrealized Loss, Total	(74)	(15)
Estimated Fair Value, Total	1,481	345
Fixed-Maturity Securities [Member] | Redeemable Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss, Less than Twelve Months	(1)
Estimated Fair Value, Less than Twelve Months	35
Gross Unrealized Loss, Total	(1)
Estimated Fair Value, Total	$ 35
Fixed-Maturity Securities [Member] | U.S. Treasury and U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss, Less than Twelve Months		(3)
Estimated Fair Value, Less than Twelve Months		2,292
Gross Unrealized Loss, Total		(3)
Estimated Fair Value, Total		$ 2,292