Acquisitions and Discontinued Operations - Consolidated Assets at Fair Value on Recurring Basis (Detail) - Recurring [Member] - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
ASSETS MEASURED ON A RECURRING BASIS
Total assets on a recurring basis at fair value	$ 15,938	$ 15,139
Trust [Member] | Education Lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans	4	191
Total assets on a recurring basis at fair value	4	191
Level 3 [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total assets on a recurring basis at fair value	328	444
Level 3 [Member] | Trust [Member] | Education Lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans	4	191
Total assets on a recurring basis at fair value	$ 4	$ 191