NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Post-retirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Post-retirement Benefits
Pension expense	$ 9,300
Unamortized actuarial loss	8,000
Liability related to underfunded status of defined benefit pension plan	$ 4,600
Future expected benefits payment
2018		$ 1,714
2019		1,630
2020		1,561
2021		1,495
2022		1,364
Next 5 years		6,403
Fisher SERP | Fisher
Post-retirement Benefits
Estimated projected benefit obligation		21,500
Benefit payments		1,800	$ 1,700
Periodic pension expense		800	900
Actuarial gain		$ 1,000	$ 100
Discount rate for projected benefit obligation (as a percent)		3.46%	3.89%
Fisher SERP | Fisher | Accrued expenses
Post-retirement Benefits
Estimated projected benefit obligation		$ 1,700
Fisher SERP | Fisher | Other long-term liabilities
Post-retirement Benefits
Estimated projected benefit obligation		$ 19,800