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

Derivative Instruments and Hedging Activities Schedule of Average Notional Amounts of Derivative Positions (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Inverse Interest-Only Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	$ 1,330,835
Derivative Liability, Notional Amount	0
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	0
Derivative Liability, Notional Amount	6,366,593	1,300,000
Credit Default Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	541,888
Derivative Liability, Notional Amount	137,567
Interest Rate Swaption [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	3,573,077
Derivative Liability, Notional Amount	0
Other Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	207,418
Derivative Liability, Notional Amount	754,396
Forward Sale Commitment [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	5,186
Derivative Liability, Notional Amount	$ 0