FAIR VALUE MEASUREMENTS FAIR VALUE MEASUREMENTS - Financial Assets and Liabilities Not Measured on Recurring Basis (Details) - Nonrecurring - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Balance
Financial Assets:
Cash and cash equivalents	$ 398,419	$ 362,025
Time deposits and restricted cash	916	3,042
Employee loans	5,669	5,978
Balance | Revolving Credit Facility
Financial Liabilities:
Borrowing under 2014 Credit Facility	25,022	25,019
Estimated Fair Value
Financial Assets:
Cash and cash equivalents	398,419	362,025
Time deposits and restricted cash	916	3,042
Employee loans	5,669	5,978
Estimated Fair Value | Revolving Credit Facility
Financial Liabilities:
Borrowing under 2014 Credit Facility	25,022	25,019
Estimated Fair Value | Level 1
Financial Assets:
Cash and cash equivalents	398,419	362,025
Time deposits and restricted cash	0	0
Employee loans	0	0
Estimated Fair Value | Level 1 | Revolving Credit Facility
Financial Liabilities:
Borrowing under 2014 Credit Facility	0	0
Estimated Fair Value | Level 2
Financial Assets:
Cash and cash equivalents	0	0
Time deposits and restricted cash	916	3,042
Employee loans	0	0
Financial Liabilities:
Borrowing under 2014 Credit Facility	25,022	25,019
Estimated Fair Value | Level 3
Financial Assets:
Cash and cash equivalents	0	0
Time deposits and restricted cash	0	0
Employee loans	5,669	5,978
Estimated Fair Value | Level 3 | Revolving Credit Facility
Financial Liabilities:
Borrowing under 2014 Credit Facility	$ 0	$ 0