Fair Value Measurement of Assets and Liabilities - Schedule of Gains and Losses from Fair Value Changes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	$ 14,096	$ 4,200	$ 26,954	$ 6,378
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		(550)		(550)
Trading (losses) gains, net [Member] | Trading Securities [Member]
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	(36)	(151)	(66)	101
Trading (losses) gains, net [Member] | Junior subordinated debentures [Member]
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	(234)	1,760	(2,406)	520
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	$ 14,366	$ 3,141	$ 29,426	$ 6,307