Effect of Other Derivative Contracts on the Consolidated Statements of Operations and Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Derivative Instruments:
Unrealized Gain (Loss)	$ 2,002,200		$ (32,219)	$ (1,815,107)
Amount of Gain/(Loss) Recognized in Income on Derivatives	(19,171)
Other Derivative Contracts | TBA Derivatives
Derivative Instruments:
Realized Gain (Loss)	33,728	[1]
Unrealized Gain (Loss)	6,630	[1]
Amount of Gain/(Loss) Recognized in Income on Derivatives	40,358	[1]
Other Derivative Contracts | Interest Rate Swaption
Derivative Instruments:
Realized Gain (Loss)	(2,697)
Unrealized Gain (Loss)	(15,467)
Amount of Gain/(Loss) Recognized in Income on Derivatives	(18,164)
Other Derivative Contracts | Us Treasury futures
Derivative Instruments:
Realized Gain (Loss)	(38,514)
Unrealized Gain (Loss)	(2,851)
Amount of Gain/(Loss) Recognized in Income on Derivatives	$ (41,365)

[1] Includes options on TBA securities