SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Impact of Topic 606 Adoption on Unaudited Condensed Consolidated Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income (loss)	$ 57,455	$ 93,637	$ 3,697	$ 104,300
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	$ 26,592	$ 28,777	79,752	85,732
Changes in operating assets and liabilities:
Accounts receivable			(11,557)	36,097
Other, net			(7,634)	(2,689)
Deferred revenue, net			5,160	$ (39,671)
Balances Without Adoption of Topic 606
Cash flows from operating activities:
Net income (loss)			(10,064)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization			78,767
Changes in operating assets and liabilities:
Accounts receivable			(2,755)
Other, net			(1,634)
Deferred revenue, net			5,104
Accounting Standard Update 2014-09 | Effect of Change Increase / (Decrease)
Cash flows from operating activities:
Net income (loss)			13,761
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization			985
Changes in operating assets and liabilities:
Accounts receivable			(8,802)
Other, net			(6,000)
Deferred revenue, net			$ 56