TWO Quarterly report pursuant to Section 13 or 15(d)

Available-for-Sale Securities, at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at fair value	$ 17,318,697	$ 13,128,857
Available-for-sale Securities Pledged as Collateral	17,149,824	13,117,329
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	10,880,230	2,742,630
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at fair value	4,023,228	8,274,507
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at fair value	216,427	209,337
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at fair value	$ 2,198,812	$ 1,902,383