Acquisitions and Discontinued Operations - Consolidated Assets and Liabilities at Fair Value on Recurring Basis (Detail) (Recurring [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
ASSETS MEASURED ON A RECURRING BASIS
Total assets at fair value	$ 14,334	$ 18,688
LIABILITIES MEASURED ON A RECURRING BASIS
Total liabilities on a recurring basis at fair value	1,148	1,700
Segment, discontinued operations [Member] | Education lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans	157
Trust loans	2,369
Trust other assets	26
Total assets at fair value	2,552
LIABILITIES MEASURED ON A RECURRING BASIS
Trust securities	2,159
Trust other liabilities	22
Total liabilities on a recurring basis at fair value	2,181
Level 1 [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total assets at fair value	99	192
LIABILITIES MEASURED ON A RECURRING BASIS
Total liabilities on a recurring basis at fair value	55	102
Level 1 [Member] | Segment, discontinued operations [Member] | Education lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans
Trust loans
Trust other assets
Total assets at fair value
LIABILITIES MEASURED ON A RECURRING BASIS
Trust securities
Trust other liabilities
Total liabilities on a recurring basis at fair value
Level 2 [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total assets at fair value	14,808	19,119
LIABILITIES MEASURED ON A RECURRING BASIS
Total liabilities on a recurring basis at fair value	1,894	2,547
Level 2 [Member] | Segment, discontinued operations [Member] | Education lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans
Trust loans
Trust other assets
Total assets at fair value
LIABILITIES MEASURED ON A RECURRING BASIS
Trust securities
Trust other liabilities
Total liabilities on a recurring basis at fair value
Level 3 [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total assets at fair value	697	829
LIABILITIES MEASURED ON A RECURRING BASIS
Total liabilities on a recurring basis at fair value	2	29
Level 3 [Member] | Segment, discontinued operations [Member] | Education lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans	157
Trust loans	2,369
Trust other assets	26
Total assets at fair value	2,552
LIABILITIES MEASURED ON A RECURRING BASIS
Trust securities	2,159
Trust other liabilities	22
Total liabilities on a recurring basis at fair value	$ 2,181