Investments - Summary of Investment Portfolio (Detail) - Credit Concentration Risk	12 Months Ended
	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	100.00%
Other
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	1.00%
Fixed maturities | Corporates | Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	80.00%
Fixed maturities | Corporates | Below Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	4.00%
Fixed maturities | Securities of state and municipal governments [Member] | Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	9.00%
Fixed maturities | Government-sponsored enterprises [Member] | Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	2.00%
Fixed maturities | Other | Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	1.00%
Fixed maturities | Other | Below Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	0.00%
Policy loans
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	3.00%