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
	Mar. 31, 2013	Mar. 31, 2012
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	$ 12,858	$ 2,178
Trading losses, net [Member] | Trading Securities [Member]
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	(30)	252
Trading losses, net [Member] | Junior subordinated debentures [Member]
Gains And Losses From Fair Value Changes [Line Items]
Gains (Losses) on Change in Fair Value	(2,172)	(1,240)
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	$ 15,060	$ 3,166