FAIR VALUE MEASUREMENTS (Financial Assets and Liabilities Not Measured on Recurring Basis) (Details) - Nonrecurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Balance
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	$ 582,585	$ 362,025
Time Deposits and Restricted Cash and Cash Equivalents, Fair Value Disclosure	673	3,042
Loans Receivable, Fair Value Disclosure	4,210	5,978
Balance | Revolving Credit Facility | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	25,009
Balance | Revolving Credit Facility | 2014 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings		25,019
Estimated Fair Value
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	582,585	362,025
Time Deposits and Restricted Cash and Cash Equivalents, Fair Value Disclosure	673	3,042
Loans Receivable, Fair Value Disclosure	4,210	5,978
Estimated Fair Value | Revolving Credit Facility | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	25,009
Estimated Fair Value | Revolving Credit Facility | 2014 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings		25,019
Estimated Fair Value | Level 1
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	582,585	362,025
Time Deposits and Restricted Cash and Cash Equivalents, Fair Value Disclosure	0	0
Loans Receivable, Fair Value Disclosure	0	0
Estimated Fair Value | Level 1 | Revolving Credit Facility | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	0
Estimated Fair Value | Level 1 | Revolving Credit Facility | 2014 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings		0
Estimated Fair Value | Level 2
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Time Deposits and Restricted Cash and Cash Equivalents, Fair Value Disclosure	673	3,042
Loans Receivable, Fair Value Disclosure	0	0
Estimated Fair Value | Level 2 | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	25,009
Estimated Fair Value | Level 2 | 2014 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings		25,019
Estimated Fair Value | Level 3
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Time Deposits and Restricted Cash and Cash Equivalents, Fair Value Disclosure	0	0
Loans Receivable, Fair Value Disclosure	4,210	5,978
Estimated Fair Value | Level 3 | Revolving Credit Facility | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	$ 0
Estimated Fair Value | Level 3 | Revolving Credit Facility | 2014 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings		$ 0