Balance and Financial Rating Related to Reinsurers (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables	$ 668	$ 646
Protective Life Insurance Company
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables	$ 184
A.M. Best Rating	A+ (superior)
Munich American Reassurance Company
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables	$ 155
A.M. Best Rating	A+ (superior
Employers Reassurance Corporation
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables	$ 91
A.M. Best Rating	A- (excellent)
General Re Life Corporation
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables	$ 90
A.M. Best Rating	A++ (superior)
All Others
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables	$ 148
A.M. Best Rating	A+ to B++ (superior to good)