Portion of Net Gains (Losses) Attributable to Level 3 Assets and Liabilities Still Held Included in Net Income (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
Residential Loans at Fair Value
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	$ (59,649)		$ (59,641)
Commercial Loans at Fair Value
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		111		122
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	31,354	10,585	30,866	43,019
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	(1,642)	(303)	(1,665)	(635)
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		(195)		(1,090)
Mortgage Servicing Rights
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	9,450	(476)	9,532	(482)
Asset-backed Securities | Acacia
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		$ (12,973)		$ (45,026)