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Contractual interest rate for funds borrowed, under the debt agreement.

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DEBT (Schedule of Debt) (Details) - USD ($) $ in Thousands	12 Months Ended
DEBT (Schedule of Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Oct. 20, 2016	Apr. 01, 2015
Debt Instrument [Line Items]
Debt Issuance Cost	$ 1,392	$ 1,491
Long-term debt
Long-term Debt and Capital Lease Obligations, Including Current Maturities	702,660	704,247
Less current portion	111	111
Long-term debt, less current portion (Note 9)	702,549	704,136
Short-term debt
Amounts due banks, interest at 31.8% in 2017	0	2,020
Current portion of long-term debt (Note 9)	111	111
Total short-term debt	111	2,131
Total debt	$ 702,660	$ 706,267
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	31.80%
Senior Notes 2015 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 350,000
Weighted Average [Member]
Debt Instrument [Line Items]
Debt Instrument, Term	15 years
Senior Notes [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	3.30%
Long-term debt
Long-term Debt and Capital Lease Obligations, Including Current Maturities	$ 691,877	$ 693,424
Other borrowings due through 2023, interest up to 8.0%
Long-term debt
Long-term Debt and Capital Lease Obligations, Including Current Maturities	$ 10,783	$ 10,823
Senior Notes 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 350,000
Minimum
Short-term debt
Derivative, Variable Interest Rate	3.10%
Minimum \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.80%
Maximum
Short-term debt
Derivative, Variable Interest Rate	4.40%
Maximum \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Maximum \| Other borrowings due through 2023, interest up to 8.0%
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.00%
Senior Notes Series A [Member] \| Senior Notes 2015 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100,000
Debt Instrument, Maturity Date	Aug. 20, 2025
Debt Instrument, Interest Rate, Stated Percentage	3.15%
Senior Notes Series A [Member] \| Senior Notes 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100,000
Debt Instrument, Maturity Date	Oct. 20, 2028
Debt Instrument, Interest Rate, Stated Percentage	2.75%
Senior Notes Series B [Member] \| Senior Notes 2015 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100,000
Debt Instrument, Maturity Date	Aug. 20, 2030
Debt Instrument, Interest Rate, Stated Percentage	3.35%
Senior Notes Series B [Member] \| Senior Notes 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100,000
Debt Instrument, Maturity Date	Oct. 20, 2033
Debt Instrument, Interest Rate, Stated Percentage	3.03%
Senior Notes Series C [Member] \| Senior Notes 2015 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 50,000
Debt Instrument, Maturity Date	Apr. 01, 2035
Debt Instrument, Interest Rate, Stated Percentage	3.61%
Senior Notes Series C [Member] \| Senior Notes 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100,000
Debt Instrument, Maturity Date	Oct. 20, 2037
Debt Instrument, Interest Rate, Stated Percentage	3.27%
Senior Notes Series D [Member] \| Senior Notes 2015 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100,000
Debt Instrument, Maturity Date	Apr. 01, 2035
Debt Instrument, Interest Rate, Stated Percentage	4.02%
Senior Notes Series D [Member] \| Senior Notes 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 50,000
Debt Instrument, Maturity Date	Oct. 20, 2041
Debt Instrument, Interest Rate, Stated Percentage	3.52%
Designated as Hedging Instruments \| Interest Rate Swap [Member]
Short-term debt
Derivative, Notional Amount	$ 125,000