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

Trading Securities, at Fair Value (Notes)	3 Months Ended
Trading Securities, at Fair Value (Notes)	Mar. 31, 2013
Trading Securities, at Fair Value [Abstract]
Trading Securities, at Fair Value	Trading Securities, at Fair Value The Company holds U.S. Treasuries in a taxable REIT subsidiary and classifies these securities as trading instruments due to short-term investment objectives. As of March 31, 2013 and December 31, 2012, the Company held U.S. Treasuries with an amortized cost of $1.0 billion and a fair value of $1.0 billion for both periods classified as trading securities. The unrealized gains included within trading securities were $5.1 million and $5.0 million as of March 31, 2013 and December 31, 2012, respectively. The Company did not sell any trading securities during the three months ended March 31, 2013 and 2012. For the three months ended March 31, 2013 and 2012, trading securities experienced unrealized gains of $17,133 and unrealized losses of $1.2 million, respectively. Unrealized gains and losses are recorded as a component of gains on investment securities, net in the Company's condensed consolidated statements of comprehensive income. At March 31, 2013, the Company pledged trading securities with a carrying value of $1.0 billion as collateral for repurchase agreements. See Note 15 - Repurchase Agreements.