SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents		$ 750,887	$ 841,021	$ 880,129
Restricted cash included in prepaid expenses and other current assets		1,534	3,320	4,932
Restricted cash included in other non-current assets		236	387	420
Cash, cash equivalents and restricted cash	[1]	$ 752,657	$ 844,728	$ 885,481	$ 874,906

[1] The following table provides a reconciliation of cash, cash equivalents and restricted cash shown above to amounts reported within the consolidated balance sheets as of December 31, 2019, 2018 and 2017 (in thousands):   December 31, 2019   December 31, 2018   December 31, 2017 Cash and cash equivalents $ 750,887
  $ 841,021
  $ 880,129
Restricted cash included in prepaid expenses and other current assets 1,534
  3,320
  4,932
Restricted cash included in other non-current assets 236
  387
  420
Cash, cash equivalents and restricted cash $ 752,657
  $ 844,728
  $ 885,481