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	9 Months Ended
	Sep. 30, 2012 Y
Fixed Maturity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected maturity date in years	4.6
Private offering price per share	$ 101.49
Fixed Maturity Securities [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected maturity date in years	3.6
Private offering price per share	$ 60.00
Fixed Maturity Securities [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected maturity date in years	5.6
Private offering price per share	$ 105.00
Fixed Maturity Securities [Member] | Discounted Cash Flow [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	$ 98
Valuation Technique(s)	Discounted cash flow
Fixed Maturity Securities [Member] | Market Approach [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	61
Valuation Technique(s)	Market approach
Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private offering price per share	$ 583.95
EBITDA projection	80	[1]
EBITDA multiple	1.82	[1]
Equity Securities [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private offering price per share	$ 0.10
Equity Securities [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private offering price per share	$ 3,842.00
Equity Securities [Member] | Market Approach [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	33
Valuation Technique(s)	Market approach
Equity Securities [Member] | Income Approach Valuation Technique [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	17
Valuation Technique(s)	Income approach
Life Settlement Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Discount rate risk premium	9.00%
Mortality assumption	185.00%
Life Settlement Contracts [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortality assumption	65.00%
Life Settlement Contracts [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortality assumption	928.00%
Life Settlement Contracts [Member] | Discounted Cash Flow [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Assets	$ 113
Valuation Technique(s)	Discounted cash flow

[1] Earnings before interest, tax, depreciation and amortization