Real Estate Securities - Activity of Credit Component of Other-than-Temporary Impairments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Activity of the Credit Component of Other-than-Temporary Impairments
Balance at beginning of period	$ 32,949	$ 35,786	$ 33,849	$ 37,149
Initial credit impairments	0	190	0	261
Subsequent credit impairments	0	28	0	70
Securities sold, or expected to sell	(253)	(904)	(348)	(904)
Securities with no outstanding principal at period end	0	(844)	(805)	(2,320)
Balance at End of Period	$ 32,696	$ 34,256	$ 32,696	$ 34,256