SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE - Repurchase Agreements Grouped by Counterparty (Detail) (USD $) In Thousands, unless otherwise specified			9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Citigroup Global Markets [Member]	Sep. 30, 2012 Jp Morgan Chase [Member]	Sep. 30, 2012 Dean Witter / Morgan Stanley [Member]	Sep. 30, 2012 Credit Suisse First Boston [Member]
Repurchase Agreement Counterparty [Line Items]
Repurchase agreements, interest ranging from 2.45% to 3.55% (December 31, 2011 - 2.50% to 4.40%)	$ 900,000	$ 1,000,000	$ 300,000	$ 200,000	$ 100,000	$ 300,000
Weighted-Average Maturity			49 months	52 months	60 months	62 months