Fair Value Measurement of Assets and Liabilities - Schedule of Gains and Losses from Fair Value Changes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	$ 44,544	$ (6,998)		$ 1,052
Net impairment losses on securities [Member] | Available For Sale Securities [Member]
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	(5,247)	(19,968)	[1]	(4,642)
Trading gains (losses), net [Member] | Trading Securities [Member]
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	219	1,015		(1,056)
Trading gains (losses), net [Member] | Junior Subordinated Debentures [Member]
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	2,574	1,256		(5,841)
Gains on sales of loans, net [Member] | Loans held for sale [Member]
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	$ 46,998	$ 10,699		$ 12,591

[1] Includes $18.3 million related to impaired trust preferred securities transferred from held-to-maturity to available for sale at December 31, 2011.