Components of Mortgage Banking Activities, Net (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
Income from MSRs, net:
MSRs	$ 8,827		$ (527)		$ 9,169		$ (544)
Sequoia IO securities	36,336		(5,363)		38,265		(4,674)
Risk management derivatives	49,544		(3,282)		50,567		(6,398)
Net market valuation adjustments	52,957		(9,172)		91,121		(11,616)
Mortgage Banking Activities, Net	58,531		(3,607)		104,552		1,324
Residential Loans at Fair Value
Income from MSRs, net:
Loans, at fair value	(41,405)				(6,535)
Commercial Loans at Fair Value
Income from MSRs, net:
Loans, at fair value	(345)				(345)
Mortgage Banking Activities
Income from MSRs, net:
Income	1,943		123		2,794		137
Late charges	11		1		18		1
Cost of sub-servicer	(234)		(30)		(412)		(34)
Income from MSRs, net:	1,720		94		2,400		104
MSRs	8,827		(527)		9,169		(544)
Sequoia IO securities	36,336		(5,363)		38,265		(4,674)
Risk management derivatives	49,544	[1]	(3,282)	[1]	50,567	[1]	(6,398)	[1]
Net market valuation adjustments	52,957		(9,172)		91,121		(11,616)
Mortgage Banking Activities, Net	58,531		(3,607)		104,552		1,324
Mortgage Banking Activities | Residential Loans at Fair Value
Income from MSRs, net:
Loans, at fair value	(41,405)				(6,535)
Mortgage Banking Activities | Commercial Loans at Fair Value
Income from MSRs, net:
Loans, at fair value	(345)				(345)
Mortgage Banking Activities | Residential Loans
Income from MSRs, net:
Net gains on loan sales			5,471				12,836
Mortgage Banking Activities | Commercial Loans
Income from MSRs, net:
Net gains on commercial loan originations					40
Net gains on loan sales	$ 3,854				$ 10,991

[1] Represents market valuations of derivatives that are used to manage risks associated with our accumulation of residential and commercial loans.