Capitalized Servicing Assets - Additional Information (Detail) - USD ($)			12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2013
Servicing Assets at Fair Value [Line Items]
Residential mortgage loans securitized formerly held in Company's portfolio				$ 1,300,000,000
Automobile loans securitized and sold			$ 0	1,400,000,000
Residential Mortgage Loans [Member]
Servicing Assets at Fair Value [Line Items]
Mortgage loans serviced for others	$ 61,700,000,000	$ 67,200,000,000	61,700,000,000	72,400,000,000
Estimated fair value of capitalized mortgage loan servicing assets	$ 249,000,000	$ 228,000,000	249,000,000
Weighted average discount rates used to estimate fair value of capitalized mortgaged loan servicing assets	12.40%	11.90%
Weighted-average option-adjusted spread in the discount rate	1119 basis points	1065 basis points
Residential Mortgage Sub Servicing Loan [Member]
Servicing Assets at Fair Value [Line Items]
Mortgage loans serviced for others	$ 37,800,000,000	$ 42,100,000,000	37,800,000,000	46,600,000,000
Commercial Mortgage Loans [Member]
Servicing Assets at Fair Value [Line Items]
Mortgage loans serviced for others	11,000,000,000	11,300,000,000	11,000,000,000	$ 11,400,000,000
Estimated fair value of capitalized mortgage loan servicing assets	$ 99,000,000	$ 87,000,000	$ 99,000,000
Weighted average discount rates used to estimate fair value of capitalized mortgaged loan servicing assets	18.00%	18.00%