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BASIS OF PRESENTATION - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Jan. 01, 2018	Jan. 01, 2016
Recent accounting pronouncements
Equity investments with readily determinable fair values	$ 200	$ 200	$ 200
Accumulated other comprehensive income	(1,282)	(1,282)	(1,609)
Retained earnings	555,806	555,806	563,593
Cumulative effect adjustment due to adoption of new accounting				$ 2,636
ASU 2016-01
Recent accounting pronouncements
Equity investments that do not have readily determinable fair values						$ 20,100
Equity investments with readily determinable fair values						600
ASU 2018-15 \| Early Adoption
Recent accounting pronouncements
Capitalized implementation costs	2,500	2,500	$ 1,200
Amortization of implementation costs	$ 100	$ 100
Adjustment \| ASU 2016-01
Recent accounting pronouncements
Accumulated other comprehensive income						(200)
Retained earnings						$ 200
Adjustment \| ASU 2018-02 \| Early Adoption
Recent accounting pronouncements
Accumulated other comprehensive income					$ (800)
Retained earnings					800
Valuation allowance					800
Cumulative effect adjustment due to adoption of new accounting					$ 0