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

Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance (Details)

Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (17,529)	$ 95,345	$ (40,906)
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(345,647)	245,229	(159,775)
Gain (loss) on mortgage loans held-for-sale	17,297two_GainLossonMortgageLoansHeldforSale	(33,846)two_GainLossonMortgageLoansHeldforSale	2,270two_GainLossonMortgageLoansHeldforSale
Trading Gain (Loss)	(358,447)us-gaap_TradingGainsLosses	320,559us-gaap_TradingGainsLosses	(198,311)us-gaap_TradingGainsLosses
Forward Sale Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on mortgage loans held-for-sale	0	0	(26)
Agency To-be-Announced Securities, Non-Risk Management [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(4,701)	38,297	0
Inverse Interest-Only Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	55,028	(13,415)	41,706
Credit Default Swap, Buying Protection [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	11,988
Forward Purchase Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on mortgage loans held-for-sale	4,729	(20,015)	2,396
Interest Rate Risk Associated with the Investment Portfolio [Member] \| Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(69,921)	151,021	(30,897)
Interest Rate Risk Associated with the Investment Portfolio [Member] \| Options Held [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(14,070)	7,798	0
Interest Rate Risk Associated with the Investment Portfolio [Member] \| Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	6,340	(11,438)	0
Interest Rate Risk Associated with the Investment Portfolio [Member] \| Short US Treasury Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(8)	(991)	(1,768)
Interest Rate Risk Associated with the Investment Portfolio [Member] \| Interest Rate Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(242,795)	123,033	(35,012)
Interest Rate Risk Associated with the Investment Portfolio [Member] \| Total Return Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	8,061	(1,087)	0
Interest Rate Risk Associated with the Investment Portfolio [Member] \| Short [Member] \| Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	201,536	(14,472)	0
Interest Rate Risk Associated with the Investment Portfolio [Member] \| Long [Member] \| Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(114,121)	6,400	(13,056)
Interest Rate Risk Associated with Borrowings [Member] \| Long [Member] \| Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(190,267)	130,268	(111,707)
Credit Risk [Member] \| Credit Default Swap, Selling Protection [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 1,742	$ (74,840)	$ (61,935)