Fair Value Measurements (Detail) - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015
Assets:
Agency mortgage-backed securities		$ 64,862,992	$ 65,718,224
Agency debentures	[1]		152,038
Credit risk transfer securities		520,321	456,510	[1]
Non-Agency mortgage-backed securities		1,197,549
Non-Agency mortgage-backed securities		66,580,862	67,233,494
Commercial real estate debt investments	[2]	4,361,972	2,911,828	[1]
Interest rate swaps		146,285	19,642	[1]
Other derivatives		137,490	22,066
Total assets		71,226,609	70,187,030
Liabilities:
Securitized debt of consolidated VIEs		3,688,977	2,366,878	[1]
Interest rate swaps		3,208,986	1,677,571	[1]
Other derivatives		154,017	49,963
Total liabilities		7,051,980	4,094,412
Non-Agency mortgage-backed securities [Member]
Assets:
Non-Agency mortgage-backed securities		1,197,549	906,722	[1]
Level 1
Assets:
Other derivatives			12,443
Total assets			12,443
Liabilities:
Other derivatives		154,017	32,778
Total liabilities		154,017	32,778
Level 2
Assets:
Agency mortgage-backed securities		64,862,992	65,718,224
Agency debentures			152,038
Credit risk transfer securities		520,321	456,510
Non-Agency mortgage-backed securities		1,197,549
Commercial real estate debt investments		4,361,972	2,911,828
Interest rate swaps		146,285	19,642
Other derivatives		137,490	9,623
Total assets		71,226,609	70,174,587
Liabilities:
Securitized debt of consolidated VIEs		3,688,977	2,366,878
Interest rate swaps		3,208,986	1,677,571
Other derivatives			17,185
Total liabilities		$ 6,897,963	4,061,634
Level 2 | Non-Agency mortgage-backed securities [Member]
Assets:
Non-Agency mortgage-backed securities			$ 906,722

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

[2] Includes senior securitized commercial mortgage loans of consolidated VIEs carried at fair value of $4.0 billion and $2.6 billion at June 30, 2016 and December 31, 2015, respectively.