Certain Regulatory Requirements and Capital Ratios - Additional Information (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Average deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations	$ 1,600,000,000	$ 1,500,000,000
Trust Preferred Securities [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier I capital (to risk-weighted assets)	$ 60,000,000
TruPS as a basis point percentage of risk-weighted assets	5