DEBT (Details) $ in Thousands, € in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 EUR (€)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 EUR (€)
Components of the company's debt obligations
Consolidated Leverage Ratio		1.71			1.71
Consolidated Interest Coverage Ratio		16.21			16.21
Long-term obligations gross including current maturities		$ 1,153,682	$ 1,191,489
Current maturities of long-term obligations		(65,988)	(62,678)
Total long-term obligations		1,087,694	1,128,811
Deferred Finance Costs, Net, Total		2,241	2,818
Deferred debt issuance costs noncurrent		2,241	2,818
Long-term obligations including current maturities		1,151,441	1,188,671
Current maturities of long-term obligations		(65,988)	(62,678)			$ (65,309)
Long-term obligations, net of unamortized debt issuance costs		1,085,453	1,125,993			$ 1,129,238
Aggregate long-term maturities, excluding finance lease obligations
Year One		61,670
Year Two		61,337
Year Three		135,324
Year Four		239,826
Year Five		375,169
After Year Five		$ 250,404
Minimum
Components of the company's debt obligations
Consolidated Interest Coverage Ratio		3.00			3.00
Maximum
Components of the company's debt obligations
Consolidated Leverage Ratio		3.50			3.50
Unsecured lines of credit
Components of the company's debt obligations
Average borrowings		$ 34,100	$ 40,000
Average annual interest rate on short-term notes payable (as a percent)		1.60%	1.90%
Compensating balance requirement		$ 0
Revolving credit facility
Components of the company's debt obligations
Credit facility interest and fees		1,500	$ 1,500
5-year revolving credit facility maturing in July 2022
Components of the company's debt obligations
Revolving credit facility maximum borrowing capacity		300,000			€ 150.0
Amount outstanding under line of credit		25,000	0		€ 0.0		€ 69.0
Notes payable
Components of the company's debt obligations
Proceeds from debt	$ 280,000			$ 280,000
Long-term obligations gross including current maturities		168,000	224,000
Deferred Finance Costs, Net, Total		390	541
Long-term obligations including current maturities		$ 167,610	$ 223,459
Interest rate on notes (as a percent)		1.36%	1.36%		1.36%		1.36%
Floating interest rate prior to conversion to a fixed interest rate		3.20%	4.00%		3.20%		4.00%
Notes payable 0.00% - 10.90%, due in monthly and annual installments through 2028
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 19,220	$ 15,531
Long-term obligations including current maturities		$ 19,220	$ 15,531
Notes payable 0.00% - 10.90%, due in monthly and annual installments through 2028 | Minimum
Components of the company's debt obligations
Interest rate on notes (as a percent)		0.00%	0.00%		0.00%		0.00%
Notes payable 0.00% - 10.90%, due in monthly and annual installments through 2028 | Maximum
Components of the company's debt obligations
Interest rate on notes (as a percent)		10.90%	16.00%		10.90%		16.00%
Senior unsecured notes 3.2%, due in 2022
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 75,000	$ 75,000
Deferred Finance Costs, Net, Total		64	88
Long-term obligations including current maturities		$ 74,936	$ 74,912
Interest rate on notes (as a percent)		3.20%	3.20%		3.20%		3.20%
Senior unsecured notes 3.5%, due in 2023
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 125,000	$ 125,000
Deferred Finance Costs, Net, Total		144	181
Long-term obligations including current maturities		$ 124,856	$ 124,819
Interest rate on notes (as a percent)		3.50%	3.50%		3.50%		3.50%
Senior unsecured notes 0.98%, due in 2023
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 112,170	$ 114,535
Deferred Finance Costs, Net, Total		356	432
Long-term obligations including current maturities		$ 111,814	$ 114,103
Interest rate on notes (as a percent)		1.00%	1.00%		1.00%		1.00%
Senior unsecured notes 3.4%, due in 2024
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 50,000	$ 50,000
Deferred Finance Costs, Net, Total		63	76
Long-term obligations including current maturities		$ 49,937	$ 49,924
Interest rate on notes (as a percent)		3.40%	3.40%		3.40%		3.40%
Senior unsecured notes 3.5%, due in 2024
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 100,000	$ 100,000
Deferred Finance Costs, Net, Total		144	181
Long-term obligations including current maturities		$ 99,856	$ 99,819
Interest rate on notes (as a percent)		3.50%	3.50%		3.50%		3.50%
Senior unsecured notes 1.17%, due in 2024
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 224,340	$ 229,070
Deferred Finance Costs, Net, Total		742	904
Long-term obligations including current maturities		$ 223,598	$ 228,166
Interest rate on notes (as a percent)		1.20%	1.20%		1.20%		1.20%
Senior unsecured notes 3.6%, due in 2025
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 125,000	$ 125,000
Deferred Finance Costs, Net, Total		169	207
Long-term obligations including current maturities		$ 124,831	$ 124,793
Interest rate on notes (as a percent)		3.60%	3.60%		3.60%		3.60%
Senior unsecured notes 3.6%, due in 2026
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 125,000	$ 125,000
Deferred Finance Costs, Net, Total		169	208
Long-term obligations including current maturities		$ 124,831	$ 124,792
Interest rate on notes (as a percent)		3.60%	3.60%		3.60%		3.60%
Capital lease obligations
Components of the company's debt obligations
Long-term obligations gross including current maturities		$ 29,952	$ 8,353
Long-term obligations including current maturities		$ 29,952	$ 8,353