REPURCHASE ARRANGEMENTS AND SIMILAR BORROWINGS - Schedule Of Repurchase Arrangements And Similar Borrowings (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Collateral Carrying Amount	$ 13,123,757		$ 13,453,159
Agency Securities [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Collateral Carrying Amount	13,123,757		13,453,159
Accrued Interest Receivable	30,263		32,858
Borrowings Outstanding	12,482,900		12,784,238
Average Borrowing Rates (in hundredths)	0.38%		0.47%
Year-End Borrowing Rates Adjusted For Effects Of Related Derivatives Held As Cash Flow Hedges [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Average Borrowing Rates (in hundredths)	0.49%		0.65%
Borrowings With Maturities Of 30 Days Or Less [Member] | Agency Securities [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Collateral Carrying Amount	12,169,534		13,406,253
Accrued Interest Receivable	28,195		32,807
Borrowings Outstanding	11,578,211		12,739,872
Average Borrowing Rates (in hundredths)	0.38%		0.47%
Borrowings With Maturities Of 31 To 90 Days [Member] | Agency Securities [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Collateral Carrying Amount	951,966		44,060
Accrued Interest Receivable	2,068		51
Borrowings Outstanding	902,432		41,520
Average Borrowing Rates (in hundredths)	0.38%		0.57%
Collateral For Structured Financings [Member] | Agency Securities [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Collateral Carrying Amount	2,257	[1]	2,846	[1]
Accrued Interest Receivable	0	[1]	0	[1]
Borrowings Outstanding	$ 2,257	[1]	$ 2,846	[1]
Average Borrowing Rates (in hundredths)	8.09%	[1]	8.12%	[1]

[1] The maturity of structured financings is directly affected by prepayments on the related mortgage pass-through securities pledged as collateral and these financings are subject to redemption by the residual bondholders.