REVENUE - Customers Accounting for a Percentage of Total Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	[1]	Dec. 31, 2017		Dec. 31, 2016	[1]
Revenue from Contract with Customer [Abstract]
Total revenue	$ 256,357	$ 203,263	$ 196,779	$ 235,182	$ 254,605	$ 190,957	$ 186,596	$ 256,309	$ 891,581		$ 888,467	[1]	$ 762,229
Concentration risk, percentage											10.00%

[1] On January 1, 2018, the Company adopted the ASC 606 revenue recognition standard and adjusted prior periods to conform. See "Note 2. Significant Accounting Policies" for additional information.