NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Post-retirement Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Post-retirement Benefits
Post-retirement plan assets	$ 28,081	$ 22,659
Fisher SERP | Fisher
Post-retirement Benefits
Estimated projected benefit obligation	$ 19,200
Discount rate for projected benefit obligation (as a percent)	4.11%	3.46%
Benefit payments	$ 1,700	$ 1,800
Actuarial gain	1,300	(1,000)
Periodic pension expense	800	$ 800
Fisher SERP | Fisher | Accrued expenses
Post-retirement Benefits
Estimated projected benefit obligation	1,600
Fisher SERP | Fisher | Other long-term liabilities
Post-retirement Benefits
Estimated projected benefit obligation	17,600
Other Post-Retirement Plans
Post-retirement Benefits
Post-retirement plan assets	26,000
Deferred compensation plan liabilities	$ 24,100