Investments - Concentrations of Credit Risk - Investment Portfolio (Detail)	12 Months Ended
	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	100.00%
Fixed maturities available for sale
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	94.00%
Policy loans
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	3.00%
Other
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	3.00%
Corporates | Fixed maturities available for sale | Investment Grade
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	78.00%
Corporates | Fixed maturities available for sale | Below Investment Grade
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	4.00%
States, municipalities, and political subdivisions | Fixed maturities available for sale | Investment Grade
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	9.00%
States, municipalities, and political subdivisions | Fixed maturities available for sale | Below Investment Grade
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	0.00%
U.S. Government direct, guaranteed, and government-sponsored enterprises | Fixed maturities available for sale | Investment Grade
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	2.00%
U.S. Government direct, guaranteed, and government-sponsored enterprises | Fixed maturities available for sale | Below Investment Grade
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	0.00%
Other | Fixed maturities available for sale | Investment Grade
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	1.00%
Other | Fixed maturities available for sale | Below Investment Grade
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	0.00%