INVESTMENT SECURITIES - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) position	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) position	Sep. 30, 2017 USD ($)
Investments, Debt and Equity Securities [Abstract]
Percentage of debt securities considered to be of investment-grade	97.00%		97.00%
Maximum percentage of any general obligation bonds in one state			9.00%
Percent of tax exempt securities insured	2.00%		2.00%
Securities in unrealized loss positions, number of positions	1,250		1,250
Number of positions	1,520		1,520
Other-than-temporary impairments | $	$ 0.0	$ 0.0	$ 0.0	$ 0.0