SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE - Schedule of Repurchase Agreement Maturity (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Repurchase Agreement [Line Items]
Securities Sold Under Agreements To Repurchase	$ 900,000	[1]	$ 900,000	[1]
Callable Repurchase Agreements [Member]
Repurchase Agreement [Line Items]
Securities Sold Under Agreements To Repurchase	800,000
Variable Rate [Member]
Repurchase Agreement [Line Items]
Securities Sold Under Agreements To Repurchase	$ 500,000

[1] As of December 31, 2014, includes $800 million with an average rate of 3.30%, and that lenders have the right to call before their contractual maturitiesat various dates beginning on January 9, 2015. Subsequent to December 31, 2014, no lender has exercised its call option on repurchase agreements.In addition, $500 million of the $900 million is tied to variable rates.