INVESTMENT SECURITIES - Proceeds from Sales and Calls of Securities and Associated Gross Gains and Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Net realized gains on sales and calls of securities available-for-sale	$ 29,405	$ 3,258	$ 1,183
Proceeds from sales and calls of securities available-for-sale	4,148,003	989,786	111,764
Tax expense on sales and calls of securities available-for-sale	12,218	1,368	498
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains on sales and calls of securities available-for-sale	30,919	3,260	1,221
Gross realized losses on sales and calls of securities available-for-sale	(1,514)	(2)	(38)
Net realized gains on sales and calls of securities available-for-sale	$ 29,405	$ 3,258	$ 1,183