REVENUE RECOGNITION - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Jan. 01, 2018
Contracts
Contract liability	$ 17,729	$ 13,787
Net deferred tax liabilities	3,989	10,276
Retained earnings	554,363	563,593
Minority interest	$ 130,216	$ 127,937
Change | ASU 2014-09
Contracts
Contract asset			$ 1,600
Contract liability			200
Contract acquisition costs			1,500
Net deferred tax liabilities			300
Retained earnings			1,500
Minority interest			1,100
Change | ASU 2014-09 | Prepayments and other current assets
Contracts
Contract asset			1,200
Contract acquisition costs			900
Change | ASU 2014-09 | Other assets
Contracts
Contract asset			400
Contract acquisition costs			$ 600