INVESTMENT SECURITIES - Investment Securities Held to Maturity (Securities in continuous unrealized loss position) (Detail) - US States And Political Subdivisions Member [Member] - P R - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity less than twelve months fair value	$ 0	$ 0
Held to maturity less than twelve months unrealized losses	0	0
Held to maturity securities twelve months or longer fair value	130,125	132,759
Held to maturity securities twelve month or longer unrealized losses	20,502	23,431
Held to maturity unrealized loss position fair value	130,125	132,759
Held to maturity unrealized loss position aggregate losses	$ 20,502	$ 23,431