TWO Annual report pursuant to Section 13 and 15(d)

Available-for-Sale Securities, at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at fair value	$ 7,825,320	$ 14,341,102
Available-for-sale Securities Pledged as Collateral	7,767,074	14,159,315
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at fair value	1,678,814	2,418,546
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at fair value	3,602,348	6,768,875
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at fair value	691,728	2,104,896
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at fair value	$ 1,852,430	$ 3,048,785