FAIR VALUE MEASUREMENTS (Reported Amounts and Estimated Fair Values of the Financial Assets and Liabilities Requiring Fair Value Disclosure) (Details) - Nonrecurring - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Balance
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	$ 770,560	$ 582,585
Restricted cash	1,151
Time deposits and restricted cash		673
Employee loans	3,525	4,210
Balance \| Revolving Credit Facility \| 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	25,020	25,009
Estimated Fair Value
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	770,560	582,585
Restricted cash	1,151
Time deposits and restricted cash		673
Employee loans	3,525	4,210
Estimated Fair Value \| Revolving Credit Facility \| 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	25,020	25,009
Estimated Fair Value \| Level 1
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	770,560	582,585
Restricted cash	1,151
Time deposits and restricted cash		0
Employee loans	0	0
Estimated Fair Value \| Level 1 \| Revolving Credit Facility \| 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	0	0
Estimated Fair Value \| Level 2
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Restricted cash	0
Time deposits and restricted cash		673
Employee loans	0	0
Estimated Fair Value \| Level 2 \| Revolving Credit Facility \| 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	25,020	25,009
Estimated Fair Value \| Level 3
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Restricted cash	0
Time deposits and restricted cash		0
Employee loans	3,525	4,210
Estimated Fair Value \| Level 3 \| Revolving Credit Facility \| 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	$ 0	$ 0

Fair value portion of cash and cash equivalent items which are restricted as to withdrawal or usage

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- Definition

Fair value portion of cash and cash equivalent items which are restricted as to withdrawal or usage and time deposits

+ References

No definition available.

+ Details

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- References

No definition available.

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

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- References

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- Definition

Fair value portion of contractual arrangement with a lender under which borrowings can be made up to a specific amount at any point in time.

+ References

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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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