ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES AND OTHER LIABILITIES - Other liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES AND OTHER LIABILITIES
Supplemental executive retirement plan obligations	$ 18,661		$ 20,195
Long-term insurance accruals	8,437		8,713
Derivative liability	6,515		3,134
Unrecognized tax benefits, and related interest and penalties	5,523		5,458
Asset retirement obligations	1,113		980
Deferred tenant improvement allowances			8,570
Deferred rent			4,455
Other	10		65
Total other liabilities	$ 40,259	$ 38,489	$ 51,570