ACCRUED EXPENSES, OTHER CURRENT LIABILITIES AND OTHER LIABILITIES - Other liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
ACCRUED EXPENSES, OTHER CURRENT LIABILITIES AND OTHER LIABILITIES
Supplemental executive retirement plan obligations	$ 20,396	$ 21,842
Long-term insurance accruals	9,531	9,531
Deferred tenant improvement allowances	7,601	7,361
Unrecognized tax benefits	5,271	5,219
Deferred rent	4,735	4,909
Other	2,144	1,391
Total other liabilities	$ 49,678	$ 50,253