Fair Value Measurements - Additional Information Relating To Asset-Backed Securities and Collateralized Debt Obligations (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	$ 448	$ 557
Level 2 [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	227
Level 3 [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	254
Estimate of Fair Value Measurement [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	481
AAA - A Rating [Member] | Level 2 [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	224
AAA - A Rating [Member] | Level 2 [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	222
AAA - A Rating [Member] | Level 2 [Member] | Trading asset-backed securities and related collateral [Member] | Student Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	68
AAA - A Rating [Member] | Level 2 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	91
AAA - A Rating [Member] | Level 2 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Home Equity Line of Credit [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	98
AAA - A Rating [Member] | Level 2 [Member] | Subprime [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	63
AAA - A Rating [Member] | Level 2 [Member] | Commercial Mortgages [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	126
AAA - A Rating [Member] | Level 3 [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	0
AAA - A Rating [Member] | Level 3 [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	0
AAA - A Rating [Member] | Level 3 [Member] | Trading asset-backed securities and related collateral [Member] | Student Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	0
AAA - A Rating [Member] | Level 3 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	0
AAA - A Rating [Member] | Level 3 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Home Equity Line of Credit [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	0
AAA - A Rating [Member] | Level 3 [Member] | Subprime [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	0
AAA - A Rating [Member] | Level 3 [Member] | Commercial Mortgages [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	0
AAA - A Rating [Member] | Estimate of Fair Value Measurement [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	224
AAA - A Rating [Member] | Estimate of Fair Value Measurement [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	222
AAA - A Rating [Member] | Estimate of Fair Value Measurement [Member] | Trading asset-backed securities and related collateral [Member] | Student Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	68
AAA - A Rating [Member] | Estimate of Fair Value Measurement [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	91
AAA - A Rating [Member] | Estimate of Fair Value Measurement [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Home Equity Line of Credit [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	98
AAA - A Rating [Member] | Estimate of Fair Value Measurement [Member] | Subprime [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	63
AAA - A Rating [Member] | Estimate of Fair Value Measurement [Member] | Commercial Mortgages [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	126
BBB -B Rating [Member] | Level 2 [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	0
Available-for-sale securities backed by collateral	94
BBB -B Rating [Member] | Level 2 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Other [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	94
BBB -B Rating [Member] | Level 3 [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	254
Available-for-sale securities backed by collateral	0
BBB -B Rating [Member] | Level 3 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Other [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	0
BBB -B Rating [Member] | Estimate of Fair Value Measurement [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	254
Available-for-sale securities backed by collateral	94
BBB -B Rating [Member] | Estimate of Fair Value Measurement [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Other [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	94
CCC - Unrated [Member] | Level 2 [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	448
CCC - Unrated [Member] | Level 2 [Member] | Trading asset-backed securities and related collateral [Member] | Other Line Of Credit [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	130
CCC - Unrated [Member] | Level 2 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	1
CCC - Unrated [Member] | Level 2 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Home Equity Line of Credit [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	129
CCC - Unrated [Member] | Level 2 [Member] | Subprime [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	5
CCC - Unrated [Member] | Level 3 [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	0
CCC - Unrated [Member] | Level 3 [Member] | Trading asset-backed securities and related collateral [Member] | Other Line Of Credit [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	0
CCC - Unrated [Member] | Level 3 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	0
CCC - Unrated [Member] | Level 3 [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Home Equity Line of Credit [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	0
CCC - Unrated [Member] | Level 3 [Member] | Subprime [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	0
CCC - Unrated [Member] | Estimate of Fair Value Measurement [Member] | Trading asset-backed securities and related collateral [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	448
CCC - Unrated [Member] | Estimate of Fair Value Measurement [Member] | Trading asset-backed securities and related collateral [Member] | Other Line Of Credit [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	130
CCC - Unrated [Member] | Estimate of Fair Value Measurement [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	1
CCC - Unrated [Member] | Estimate of Fair Value Measurement [Member] | Alt [Member] | Trading asset-backed securities and related collateral [Member] | Home Equity Line of Credit [Member]
Fair Value Of Other Financial Instrument [Line Items]
Available-for-sale securities backed by collateral	129
CCC - Unrated [Member] | Estimate of Fair Value Measurement [Member] | Subprime [Member] | Trading asset-backed securities and related collateral [Member] | Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	$ 5