SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE - Repurchase Agreements Grouped by Counterparty (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Repurchase Agreement Counterparty [Line Items]
Maximum aggregate balance outstanding	[1],[2]	$ 700,000	$ 900,000
Citigroup Global Markets [Member]
Repurchase Agreement Counterparty [Line Items]
Maximum aggregate balance outstanding		$ 300,000
Weighted-Average Maturity		9 months 30 days
Jp Morgan Chase [Member]
Repurchase Agreement Counterparty [Line Items]
Maximum aggregate balance outstanding		$ 200,000
Weighted-Average Maturity		6 years 1 month
Dean Witter Morgan Stanley [Member]
Repurchase Agreement Counterparty [Line Items]
Maximum aggregate balance outstanding		$ 100,000
Weighted-Average Maturity		1 year 10 months
Credit Suisse First Boston [Member]
Repurchase Agreement Counterparty [Line Items]
Maximum aggregate balance outstanding		$ 100,000
Weighted-Average Maturity		7 months

[1] As of December 31, 2015, includes $600 million with an average rate of 2.73%, and that lenders have the right to call before their contractual maturitiesat various dates beginning on January 11, 2016. Subsequent to December 31, 2015, 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 ASC210-20-45-11.