Fair Value - Quantitative Information about Significant Unobservable Inputs Utilized by Company in Fair Value Measurements of Level 3 Assets (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Fixed Maturity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit spread adjustment	4.00%	6.00%
Fixed Maturity Securities [Member] | Discounted Cash Flow [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value	$ 142	$ 138
Valuation Techniques	Discounted cash flow
Fixed Maturity Securities [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit spread adjustment	0.00%	3.00%
Fixed Maturity Securities [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit spread adjustment	20.00%	184.00%
Life Settlement Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Discount rate risk premium	9.00%	9.00%
Mortality assumption	164.00%	164.00%
Life Settlement Contracts [Member] | Discounted Cash Flow [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value	$ 72	$ 74
Valuation Techniques	Discounted cash flow
Life Settlement Contracts [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortality assumption	55.00%	55.00%
Life Settlement Contracts [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortality assumption	1676.00%	1676.00%