Deposits - Additional Information (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Aggregate amounts of deposits reclassified as loan balances	$ 3,500,000	$ 5,100,000
Brokered deposits	$ 4,000,000,000	$ 4,000,000,000
Brokered deposits, weighted average interest rates	0.32%	0.21%
Money Market
Schedule of Investments [Line Items]
Brokered deposits	$ 2,500,000,000	$ 2,600,000,000
Interest Bearing Checking Accounts
Schedule of Investments [Line Items]
Brokered deposits	1,500,000,000	1,400,000,000
Certificates of Deposits
Schedule of Investments [Line Items]
Brokered deposits	$ 0	$ 3,500,000