Portion of Net Gains (Losses) Attributable to Level 3 Assets and Liabilities Still Held Included in Net Income (Detail) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Real Estate Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gains (Losses) attributable to level 3 assets still held included in net income	$ 1,323	$ 2,978	$ 1,542	$ 7,344
Trading Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gains (Losses) attributable to level 3 assets still held included in net income	(9,557)	5,042	1,070	17,364
Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gains (Losses) attributable to level 3 assets still held included in net income	(1,466)	(4,216)	(2,469)	(6,134)
Derivative Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gains (Losses) attributable to level 3 assets still held included in net income		15		(5)
Derivative Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gains (Losses) attributable to level 3 liabilities still held included in net income		49		109
Acacia | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gains (Losses) attributable to level 3 liabilities still held included in net income	$ 17,380	$ 11,257	$ (6,757)	$ 6,004