Acquisition, Divestiture, and Discontinued Operations - Consolidated Assets at Fair Value on Recurring Basis (Detail) - Recurring [Member] - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
ASSETS MEASURED ON A RECURRING BASIS
Total assets on a recurring basis at fair value	$ 22,143	$ 15,938
Level 1 [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total assets on a recurring basis at fair value	117	149
Level 2 [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total assets on a recurring basis at fair value	22,239	16,327
Level 3 [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total assets on a recurring basis at fair value	54	85
Trust [Member] | Education Lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans	3	4
Total assets on a recurring basis at fair value	3	4
Trust [Member] | Level 1 [Member] | Education Lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans	0	0
Total assets on a recurring basis at fair value	0	0
Trust [Member] | Level 2 [Member] | Education Lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans	0	0
Total assets on a recurring basis at fair value	0	0
Trust [Member] | Level 3 [Member] | Education Lending [Member]
ASSETS MEASURED ON A RECURRING BASIS
Portfolio loans	3	4
Total assets on a recurring basis at fair value	$ 3	$ 4