INVESTMENT SECURITIES - Proceeds from Sales and Calls of Securities and Associated Gross Gains and Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Net realized gains on sales and calls of securities available-for-sale	$ 3,356	$ 16,789
Proceeds from sales and calls of securities available-for-sale	378,539	2,247,421
Tax expense on sales and calls of securities available-for-sale	1,396	7,060
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains on sales and calls of securities available-for-sale	3,356	16,794
Gross realized losses on sales and calls of securities available-for-sale	0	(5)
Net realized gains on sales and calls of securities available-for-sale	$ 3,356	$ 16,789