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EMPLOYEE BENEFIT PLANS (Employee 401(k) Plan, Employee Pension Plan, Registered Retirement Savings Plan and Employee Stock Purchase Plan) (Details) - USD ($) |  | 12 Months Ended
--- | --- | ---
Sep. 15, 2015 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Maximum annual employee contribution |  | 4.00% | 4.00% | 4.00%
Company match to employee contributions |  | $ 12,000,000 | $ 12,000,000 | $ 10,000,000
Administrative expense |  | $ 0 | 0 | 0
Maximum percentage of employee total compensation matched by employer (in hundredths) |  | 100.00% |  |
Registered Retirement Savings Plan |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Maximum annual employee contribution |  | 4.00% |  |
Company match to employee contributions |  | $ 70,000 | $ 58,000 | $ 43,000
Maximum percentage of employee total compensation matched by employer (in hundredths) |  | 100.00% | 100.00% | 100.00%
Employee Stock Purchase Plan |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Percentage of purchase price of company's common stock to the market price |  | 90.00% |  |
Increase in shares of common stock issued pursuant to stock plan (in shares) | 100,000 |  |  |
Shares available, employee stock purchase plan (in shares) |  | 51,584 | 65,174 |
Shares of Company's common stock purchased during the period (in shares) |  | 13,590 | 14,848 |
Foreign Plan | Pension Plan |  |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |  |
Company match to employee contributions |  | $ 600,000 | $ 500,000 | $ 400,000
Maximum percentage of employee total compensation matched by employer (in hundredths) |  | 6.00% | 6.00% | 6.00%

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