SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE - Repurchase Agreements Grouped by Counterparty (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Repurchase Agreement Counterparty [Line Items]
Repurchase agreements, interest ranging from 2.45% to 3.39% (December 31, 2011 - 2.50% to 4.40%) (1)	[1],[2]	$ 700,000	$ 700,000
Citigroup Global Markets [Member]
Repurchase Agreement Counterparty [Line Items]
Repurchase agreements, interest ranging from 2.45% to 3.39% (December 31, 2011 - 2.50% to 4.40%) (1)		$ 300,000
Weighted-Average Maturity		7 months
Jp Morgan Chase [Member]
Repurchase Agreement Counterparty [Line Items]
Repurchase agreements, interest ranging from 2.45% to 3.39% (December 31, 2011 - 2.50% to 4.40%) (1)		$ 200,000
Weighted-Average Maturity		5 years 10 months
Dean Witter Morgan Stanley [Member]
Repurchase Agreement Counterparty [Line Items]
Repurchase agreements, interest ranging from 2.45% to 3.39% (December 31, 2011 - 2.50% to 4.40%) (1)		$ 100,000
Weighted-Average Maturity		1 year 7 months
Credit Suisse First Boston [Member]
Repurchase Agreement Counterparty [Line Items]
Repurchase agreements, interest ranging from 2.45% to 3.39% (December 31, 2011 - 2.50% to 4.40%) (1)		$ 100,000
Weighted-Average Maturity		3 months 29 days

[1] As of March 31, 2016, includes $600 million with an average rate of 2.88% that lenders have the right to call before their contractual maturities at various dates beginning on July 19, 2016. Subsequent to March 31, 2016, no lender has exercised its call option on repurchase agreements. In addition, $500 million is tied to variable rates.

[2] Reported net of securities purchased under agreements to repurchase (reverse repurchase agreements) by counterparty, when applicable, pursuant to ASC 210-20-45-11.