TWO Annual report pursuant to Section 13 and 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	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Inverse Interest-Only Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	$ 1,741,380	$ 885,734
Derivative Liability, Average Notional Amount	0	0
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	0	0
Derivative Liability, Average Notional Amount	9,891,749	3,667,493
Credit Default Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	563,434	250,894
Derivative Liability, Average Notional Amount	68,541	135,952
Interest Rate Swaption [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	4,023,639	1,619,452
Derivative Liability, Average Notional Amount	0	0
Other Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	546,429	313,630
Derivative Liability, Average Notional Amount	526,085	726,781
Short US Treasury Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	0	0
Derivative Liability, Average Notional Amount	11,749	0
Forward Purchase Commitment [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	94,855	0
Derivative Liability, Average Notional Amount	0	0
Forward Sale Commitment [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	2,395	128
Derivative Liability, Average Notional Amount	$ 0	$ 0