Acquisitions and Discontinued Operations - Components of Assets of Education Lending Business (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans at fair value	$ 3	$ 4
Loans, net of unearned income	62,098	59,876	$ 58,264
Loans held for sale at fair value	0	0	0
Total assets	1,717	1,846	2,169
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans, net of unearned income	1,689	1,824	1,962
Less: Allowance for loan and lease losses	20	28	22
Net loans	1,672	1,800	1,940
Accrued income and other assets	29	30	34
Total assets	1,717	1,846	2,169
Portfolio [Member] | Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans at fair value	3	4
Loans held for sale at fair value			179
Education Lending [Member] | Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Held-to-maturity securities	1	1	1
Loans, net of unearned income	1,689	1,824	1,962
Less: Allowance for loan and lease losses	20	28	22
Net loans	1,672	1,800	1,940
Accrued income and other assets	29	30	34
Total assets	1,702	1,831	2,154
Education Lending [Member] | Portfolio [Member] | Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans at fair value	$ 3	$ 4
Loans held for sale at fair value			$ 179