Fair Value - Quantitative Information about Significant Unobservable Inputs Utilized by Company Fair Value Measurements of Level 3 Assets (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012 Y
Fixed Maturity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected call date		4.3
Credit spread adjustment	3.98%	0.17%
Private offering price		$ 100.11
Fixed Maturity Securities [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected call date		3.3
Credit spread adjustment	1.74%	0.02%
Private offering price		$ 42.39
Fixed Maturity Securities [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected call date		5.3
Credit spread adjustment	19.90%	0.48%
Private offering price		$ 102.32
Fixed Maturity Securities [Member] | Discounted Cash Flow [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	$ 142	$ 121
Valuation Technique(s)	Discounted cash flow	Discounted cash flow
Fixed Maturity Securities [Member] | Market approach [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets		72
Valuation Technique(s)		Market approach
Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private offering price	$ 1,147.95	$ 571.17
Equity Securities [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private offering price	$ 360.12	$ 4.54
Equity Securities [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private offering price	$ 4,267.66	$ 3,842.00
Equity Securities [Member] | Market approach [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	10	34
Valuation Technique(s)	Market approach	Market approach
Life Settlement Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Discount rate risk premium	9.00%	9.00%
Mortality assumption	191.60%	208.90%
Life Settlement Contracts [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortality assumption	70.00%	69.00%
Life Settlement Contracts [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortality assumption	743.00%	883.00%
Life Settlement Contracts [Member] | Discounted Cash Flow [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	$ 88	$ 100
Valuation Technique(s)	Discounted cash flow	Discounted cash flow