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	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Inverse Interest-Only Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	$ 1,735,973	$ 1,850,637
Derivative Liability, Average Notional Amount	0	0
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	19,884,272	17,486,421
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	1,525,716	913,477
Interest Rate Swaption [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	6,002,717	5,766,300
Derivative Liability, Average Notional Amount	0	0
Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	2,584,391	1,904,608
Derivative Liability, Average Notional Amount	2,270,489	1,295,974
Options Held [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	413,043	95,560
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	10,032,609	5,225,275
Short US Treasury Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	0	0
Derivative Liability, Average Notional Amount	0	8,901
Forward Purchase Commitment [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Average Notional Amount	0	0
Derivative Liability, Average Notional Amount	$ 6,672	$ 75,117