EMPLOYEE BENEFIT PLANS - Actuarial Computations to Determine Net Period Benefit Cost (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate on benefit obligations	3.48%	3.70%
Expected long-term rate of return on plan assets	6.00%	6.50%	7.00%
AB Qualified Retirement Plan
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate on benefit obligations	4.55%	4.75%	4.30%