RESIDENTIAL MORTGAGE INVESTMENTS - Additional Information (Detail) (USD $) In Billions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Schedule Of Residential Mortgage Investments [Line Items]
Mortgage securities weighted average contractual maturity, months	291
Current-Reset ARMs [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Investments held, basis amount	$ 7.41
Agency securities average months to roll, months	5 months 27 days
Current-Reset ARMs [Member] | Maximum [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Agency securities months to roll	18 months
Longer-To-Reset ARMs [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Investments held, basis amount	$ 6.10
Agency securities average months to roll, months	40 months
Longer-To-Reset ARMs [Member] | Minimum [Member]
Schedule Of Residential Mortgage Investments [Line Items]
Agency securities months to roll	18 months