SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE - Repurchase Agreements Grouped by Counterparty (Detail) - USD ($) $ in Thousands		3 Months Ended
		Sep. 30, 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]	$ 600,000	$ 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		1 month
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 4 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 1 month

[1] As of September 30, 2016, includes $500 million with an average rate of 3.56% that lenders have the right to call before their contractual maturities at various dates beginning on October 11, 2016. In addition, $400 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.