INTEREST AND DIVIDEND ON INVESTMENTS- Components of interest and dividend income on investments (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of interest and dividend income on investments [Abstract]
Interest income on investment securities and money market investments	$ 53,634	$ 52,816	$ 55,923
Dividends on FHLB stock	2,105	1,454	1,075
Total interest and dividends on investments	$ 55,739	$ 54,270	$ 56,998

The amount of interest income and other income recognized during the period. Included in this element is interest derived from investments in debt securities, cash and cash equivalents, and other investments which reflect the time value of money or transactions in which the payments are for the use or forbearance of money and other income from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business).

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration