EMPLOYEE BENEFIT PLANS - Retirement Income Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Period based on which benefits are based on the highest average compensation during last ten years	5 years
Company contributions to defined contribution plan	$ 12,100,000	$ 11,000,000	$ 10,200,000
Benefits paid	10,225,000	18,634,000
Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Company contributions to defined contribution plan	0	3,300,000	$ 5,000,000
Single-sum payment for the ability to elect for a limited time the commencement of benefit		$ 0
Benefits paid	$ 8,800,000