ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES AND OTHER LIABILITIES - Other liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES AND OTHER LIABILITIES
Supplemental executive retirement plan obligations	$ 20,751	$ 21,842
Long-term insurance accruals	9,291	9,531
Deferred tenant improvement allowances	8,265	7,361
Unrecognized tax benefits	5,404	5,219
Deferred rent	4,580	4,909
Other	1,104	1,391
Total other liabilities	$ 49,395	$ 50,253