Fair Value - Quantitative Information about Significant Unobservable Inputs Utilized by Company in Fair Value Measurements of Level 3 Assets (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Fixed Maturity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit spread adjustment	3.00%	4.00%
Fixed Maturity Securities [Member] | Discounted Cash Flow [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	$ 95	$ 142
Valuation Techniques	Discounted cash flow	Discounted cash flow
Fixed Maturity Securities [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit spread adjustment	2.00%	2.00%
Fixed Maturity Securities [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit spread adjustment	12.00%	20.00%
Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private offering price	$ 554	$ 1,148
Equity Securities [Member] | Market approach [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	18	10
Valuation Techniques	Market approach	Market approach
Equity Securities [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private offering price	$ 13	$ 360
Equity Securities [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private offering price	$ 4,388	$ 4,268
Life Settlement Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Discount rate risk premium	9.00%	9.00%
Mortality assumption	193.00%	192.00%
Life Settlement Contracts [Member] | Discounted Cash Flow [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	$ 86	$ 88
Valuation Techniques	Discounted cash flow	Discounted cash flow
Life Settlement Contracts [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortality assumption	70.00%	70.00%
Life Settlement Contracts [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortality assumption	743.00%	743.00%