Investments - Summarized Fair Value and Gross Unrealized Losses on Available-for-sale Debt Securities (Detail) $ in Thousands	Mar. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Number of issues | security	149	68
Less than 12 months, Fair value	$ 130,567	$ 79,297
Less than 12 months, Unrealized losses	$ (4,297)	$ (468)
12 months or longer, Number of issues | security	8	42
12 months or longer, Fair value	$ 4,155	$ 65,802
12 months or longer, Unrealized losses	$ (83)	$ (557)
Fixed Maturities [Member] | U.S. Government Obligations and Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Number of issues | security	0	2
Less than 12 months, Fair value	$ 0	$ 3,836
Less than 12 months, Unrealized losses	$ 0	$ (108)
12 months or longer, Number of issues | security	1	4
12 months or longer, Fair value	$ 129	$ 23,186
12 months or longer, Unrealized losses	$ (3)	$ (80)
Fixed Maturities [Member] | Corporate Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Number of issues | security	75	18
Less than 12 months, Fair value	$ 63,401	$ 16,808
Less than 12 months, Unrealized losses	$ (2,868)	$ (107)
12 months or longer, Number of issues | security	1	7
12 months or longer, Fair value	$ 215	$ 5,866
12 months or longer, Unrealized losses	$ (38)	$ (34)
Fixed Maturities [Member] | Mortgage-Backed and Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Number of issues | security	58	42
Less than 12 months, Fair value	$ 66,017	$ 58,023
Less than 12 months, Unrealized losses	$ (1,354)	$ (245)
12 months or longer, Number of issues | security	5	26
12 months or longer, Fair value	$ 3,534	$ 34,985
12 months or longer, Unrealized losses	$ (39)	$ (361)
Fixed Maturities [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Number of issues | security	0	0
Less than 12 months, Fair value	$ 0	$ 0
Less than 12 months, Unrealized losses	$ 0	$ 0
12 months or longer, Number of issues | security	1	1
12 months or longer, Fair value	$ 277	$ 276
12 months or longer, Unrealized losses	$ (3)	$ (4)
Fixed Maturities [Member] | Redeemable Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Number of issues | security	16	6
Less than 12 months, Fair value	$ 1,149	$ 630
Less than 12 months, Unrealized losses	$ (75)	$ (8)
12 months or longer, Number of issues | security	0	4
12 months or longer, Fair value	$ 0	$ 1,489
12 months or longer, Unrealized losses	$ 0	$ (78)