Investments - Concentrations of Credit Risk - Investment Portfolio (Detail)	12 Months Ended
	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	100.00%
State and municipal governments, percent of invested assets at fair value	11.00%
Texas
Debt Securities, Available-for-sale [Line Items]
State and municipal governments, percent of invested assets at fair value	22.00%
New York
Debt Securities, Available-for-sale [Line Items]
State and municipal governments, percent of invested assets at fair value	10.00%
California
Debt Securities, Available-for-sale [Line Items]
State and municipal governments, percent of invested assets at fair value	10.00%
Michigan
Debt Securities, Available-for-sale [Line Items]
State and municipal governments, percent of invested assets at fair value	7.00%
Ohio
Debt Securities, Available-for-sale [Line Items]
State and municipal governments, percent of invested assets at fair value	5.00%
Florida
Debt Securities, Available-for-sale [Line Items]
State and municipal governments, percent of invested assets at fair value	4.00%
Fixed maturities available for sale | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	94.00%
Policy loans | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	2.00%
Other | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	4.00%
Corporates | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	80.00%
Corporates | Fixed maturities available for sale | Investment Grade | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	77.00%
Corporates | Fixed maturities available for sale | Below Investment Grade | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	3.00%
States, municipalities, and political subdivisions | Fixed maturities available for sale | Investment Grade | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	11.00%
States, municipalities, and political subdivisions | Fixed maturities available for sale | Below Investment Grade | Investment portfolio | Credit Concentration Risk
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 | Investment portfolio | Credit Concentration Risk
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 | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	0.00%
Other | Fixed maturities available for sale | Investment Grade | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	1.00%
Other | Fixed maturities available for sale | Below Investment Grade | Investment portfolio | Credit Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Concentration risk percentage	0.00%