SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE - Schedule of Repurchase Agreement Maturity (Parenthetical) (Detail) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Repurchase Agreement [Line Items]
Securities Sold Under Agreements To Repurchase	[1],[2]	$ 300,000	$ 300,000
Variable Rate [Member]
Repurchase Agreement [Line Items]
Securities Sold Under Agreements To Repurchase		$ 100,000

[1] As of September 30, 2017, includes $200 million with an average rate of 2.11% that lenders have the right to call before their contractual maturities at various dates beginning on July 19, 2017. In addition, $100 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.