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

Derivative Instruments and Hedging Activities Schedule of Average Notional Amounts of Derivative Positions (Details)

Derivative Instruments and Hedging Activities Schedule of Average Notional Amounts of Derivative Positions (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
Inverse Interest-Only Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	$ 1,895,789	$ 1,908,919
Derivative Liability, Average Notional Amount	0	0
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	17,655,220	16,267,624
Derivative Liability, Average Notional Amount	0	0
Credit Default Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	0	0
Derivative Liability, Average Notional Amount	764,914	602,283
Interest Rate Swaption [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	5,748,352	5,646,133
Derivative Liability, Average Notional Amount	0	0
Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	1,959,495	1,588,630
Derivative Liability, Average Notional Amount	1,234,769	783,227
Options Held [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	130,901	65,812
Derivative Liability, Average Notional Amount	0	0
Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	0	0
Derivative Liability, Average Notional Amount	5,532,967	2,781,768
Short US Treasury Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	0	0
Derivative Liability, Average Notional Amount	26,703	13,425
Forward Purchase Commitment [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	0	0
Derivative Liability, Average Notional Amount	$ 297,207	$ 174,920