Fair Value Option Elected, Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Loans Receivable, Fair Value Disclosure	$ 222	$ 257
Trading Loans [Member]
Loans Receivable, Fair Value Disclosure	2,517	2,655
Aggregate Unpaid Principal Balance Under the Fair Value Option	(2,488)	(2,605)
Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables	29	50
Loans Held For Sale [Member]
Loans Receivable, Fair Value Disclosure	3,540	1,494
Aggregate Unpaid Principal Balance Under the Fair Value Option	(3,516)	(1,453)
Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables	24	41
Loans Held For Investment [Member] | Performing Financial Instruments [Member]
Loans Receivable, Fair Value Disclosure	219	254
Aggregate Unpaid Principal Balance Under the Fair Value Option	(225)	(259)
Fair Value, Option, Loans Held as Assets, Aggregate Difference	(6)	(5)
Loans Held For Investment [Member] | Nonperforming Financing Receivable [Member]
Loans Receivable, Fair Value Disclosure	3	3
Aggregate Unpaid Principal Balance Under the Fair Value Option	(4)	(5)
Fair Value, Option, Loans Held as Assets, Aggregate Amount in Nonaccrual Status, Aggregated Difference	(1)	(2)
Brokered Time Deposits [Member]
Obligations, Fair Value Disclosure	78
Aggregate Unpaid Principal Balance Under the Fair Value Option	(80)
Fair Value, Option, Aggregate Differences, Long-term Debt Instruments	(2)
Long-term Debt [Member]
Obligations, Fair Value Disclosure	963	973
Aggregate Unpaid Principal Balance Under the Fair Value Option	(924)	(907)
Fair Value, Option, Aggregate Differences, Long-term Debt Instruments	$ 39	$ 66