Fair Value Of Financial Instruments (Quantitative Information Regarding The Significant Unobservable Inputs For Certain Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Other Derivative Liabilities [Member] | Discounted cash flow [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, liabilities	$ 31
Discounted Cash Flows [Member] | Other Derivative Liabilities [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range dollars	0
Discounted Cash Flows [Member] | Other Derivative Liabilities [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range dollars	83
Discounted Cash Flows [Member] | Other Derivative Liabilities [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range dollars	42	[1]
Credit Derivatives [Member] | Commercial Mortgage Backed Securities [Member] | BET Model [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, liabilities	282		1,050
Credit Derivatives [Member] | Multi Sector C D O [Member] | Direct Price Model [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, liabilities	12		12
Credit Derivatives [Member] | Other Derivative Liabilities [Member] | BET And Dual Default Valuation Models [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, liabilities	15		85
Credit Derivatives [Member] | Recovery Rates [Member] | Commercial Mortgage Backed Securities [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	25.00%		25.00%
Credit Derivatives [Member] | Recovery Rates [Member] | Commercial Mortgage Backed Securities [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	90.00%		90.00%
Credit Derivatives [Member] | Recovery Rates [Member] | Commercial Mortgage Backed Securities [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	74.00%		60.00%
Credit Derivatives [Member] | Recovery Rates [Member] | Other Derivative Liabilities [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	42.00%		42.00%
Credit Derivatives [Member] | Recovery Rates [Member] | Other Derivative Liabilities [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	45.00%		90.00%
Credit Derivatives [Member] | Recovery Rates [Member] | Other Derivative Liabilities [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	45.00%		45.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	5.00%		8.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	23.00%		57.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	20.00%		25.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Multi Sector C D O [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	55.00%		57.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Multi Sector C D O [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	55.00%		57.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Multi Sector C D O [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	55.00%		57.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Other Derivative Liabilities [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	10.00%		13.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Other Derivative Liabilities [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	51.00%		54.00%
Credit Derivatives [Member] | Nonperformance Risk [Member] | Other Derivative Liabilities [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	37.00%		25.00%
Credit Derivatives [Member] | Weighted Average Life [Member] | Commercial Mortgage Backed Securities [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Weighted Average (in years)	0.9		1.1
Credit Derivatives [Member] | Weighted Average Life [Member] | Commercial Mortgage Backed Securities [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Weighted Average (in years)	3.3		28
Credit Derivatives [Member] | Weighted Average Life [Member] | Commercial Mortgage Backed Securities [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Weighted Average (in years)	2.9		3.3
Credit Derivatives [Member] | Weighted Average Life [Member] | Other Derivative Liabilities [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Weighted Average (in years)	0.2		0.2
Credit Derivatives [Member] | Weighted Average Life [Member] | Other Derivative Liabilities [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Weighted Average (in years)	8.5		8.7
Credit Derivatives [Member] | Weighted Average Life [Member] | Other Derivative Liabilities [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Weighted Average (in years)	2.2		2.3
Credit Derivatives [Member] | Commercial Mortgage Backed Securities Spreads [Member] | Commercial Mortgage Backed Securities [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	0.00%		1.00%
Credit Derivatives [Member] | Commercial Mortgage Backed Securities Spreads [Member] | Commercial Mortgage Backed Securities [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	32.00%		29.00%
Credit Derivatives [Member] | Commercial Mortgage Backed Securities Spreads [Member] | Commercial Mortgage Backed Securities [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	10.00%		13.00%
Loans Receivable [Member] | Variable Interest Entity Primary Beneficiary [Member] | Quoted market prices adjusted for financial guarantees provided to VIE obligations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, assets	1,557		1,612
Loans Receivable [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	0.00%		0.00%
Loans Receivable [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	14.00%		17.00%
Loans Receivable [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	3.00%		3.00%
Loan Repurchase Commitments [Member] | Variable Interest Entity Primary Beneficiary [Member] | Discounted cash flow [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, assets	364		359
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Quoted market prices of VIE assets adjusted for financial guarantees provided [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, liabilities	$ 812		$ 940
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Minimum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	0.00%		0.00%
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	31.00%		25.00%
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Weighted Average [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Range percentage	14.00%		12.00%

[1] Midpoint of cash flows are used for the weighted average.