Summary of Fair Value Information about Derivative Assets and Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Interest rate swaps, at fair value	$ 146,285	$ 19,642	[1]
Other derivatives, at fair value	137,490	22,066	[1]
Derivative assets	283,775	41,708
Interest rate swaps, at fair value	3,208,986	1,677,571	[1]
Other derivatives, at fair value	154,017	49,963	[1]
Derivative liabilities	3,363,003	1,727,534
Future
Derivatives, Fair Value [Line Items]
Other derivatives, at fair value		12,444
Other derivatives, at fair value	154,017	32,778
TBA Derivatives
Derivatives, Fair Value [Line Items]
Other derivatives, at fair value	$ 137,490	9,622
Other derivatives, at fair value		$ 17,185

[1] Derived from the audited consolidated financial statements at December 31, 2015.