EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined contribution plan expense	$ 4,600	$ 2,800	$ 1,400
Defined contribution plan, employer matching contribution percent	4.00%
Deferred compensation liability	$ 40,074	40,474
Carrying value of shares held in trust for stock related compensation plans	7,283	6,928
Cash surrender value of bank-owned life insurance policies	158,900	156,900
Supplemental Retirement and Salary Contribution Plans [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation plans expense	2,700	1,300	$ 1,200
Deferred compensation liability	38,300	39,000
Deferred Compensation Plans and Rabbi Trusts [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation liability	9,000	8,400
Carrying value of shares held in trust for stock related compensation plans	7,300	6,900
Shares held in Treasury for future payment	$ 7,300	$ 6,900