LONG-TERM OBLIGATIONS (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Long-Term Obligations
Long-term obligations gross including current maturities	$ 776,941	$ 778,788
Current maturities of long-term obligations	(4,258)	(4,603)
Total long-term obligations	772,683	774,185
Deferred Finance Costs, Net, Total	1,392	1,448
Deferred debt issuance costs noncurrent	1,392	1,448
Long-term obligations including current maturities	775,549	777,340
Current maturities of long-term obligations	(4,258)	(4,603)
Long-term obligations, net of unamortized debt issuance costs	771,291	772,737
Aggregate long-term maturities, excluding capital lease obligations
2017	3,513
2018	79,849
2019	2,789
2020	85,838
2021	1,726
Thereafter	601,901
Notes payable 0.61% - 16.00%, due in monthly and annual installments through 2025
Long-Term Obligations
Long-term obligations gross including current maturities	16,616	18,246
Long-term obligations including current maturities	$ 16,616	$ 18,246
Notes payable 0.61% - 16.00%, due in monthly and annual installments through 2025 | Minimum
Long-Term Obligations
Interest rate on notes (as a percent)	0.61%	0.61%
Notes payable 0.61% - 16.00%, due in monthly and annual installments through 2025 | Maximum
Long-Term Obligations
Interest rate on notes (as a percent)	16.00%	16.00%
Senior unsecured notes 6.0%, due in 2018
Long-Term Obligations
Long-term obligations gross including current maturities	$ 75,000	$ 75,000
Deferred Finance Costs, Net, Total	30	37
Long-term obligations including current maturities	$ 74,970	$ 74,963
Interest rate on notes (as a percent)	6.00%	6.00%
Senior unsecured notes 3.8%, due in 2020
Long-Term Obligations
Long-term obligations gross including current maturities	$ 84,000	$ 84,000
Deferred Finance Costs, Net, Total	113	119
Long-term obligations including current maturities	$ 83,887	$ 83,881
Interest rate on notes (as a percent)	3.80%	3.80%
Senior unsecured notes 3.2%, due in 2022
Long-Term Obligations
Long-term obligations gross including current maturities	$ 75,000	$ 75,000
Deferred Finance Costs, Net, Total	132	138
Long-term obligations including current maturities	$ 74,868	$ 74,862
Interest rate on notes (as a percent)	3.20%	3.20%
Senior unsecured notes 3.5%, due in 2023
Long-Term Obligations
Long-term obligations gross including current maturities	$ 125,000	$ 125,000
Deferred Finance Costs, Net, Total	247	256
Long-term obligations including current maturities	$ 124,753	$ 124,744
Interest rate on notes (as a percent)	3.50%	3.50%
Senior unsecured notes 3.4%, due in 2024
Long-Term Obligations
Long-term obligations gross including current maturities	$ 50,000	$ 50,000
Deferred Finance Costs, Net, Total	101	104
Long-term obligations including current maturities	$ 49,899	$ 49,896
Interest rate on notes (as a percent)	3.40%	3.40%
Senior unsecured notes 3.5%, due in 2024
Long-Term Obligations
Long-term obligations gross including current maturities	$ 100,000	$ 100,000
Deferred Finance Costs, Net, Total	247	256
Long-term obligations including current maturities	$ 99,753	$ 99,744
Interest rate on notes (as a percent)	3.50%	3.50%
Senior unsecured notes 3.6%, due in 2025
Long-Term Obligations
Long-term obligations gross including current maturities	$ 125,000	$ 125,000
Deferred Finance Costs, Net, Total	261	269
Long-term obligations including current maturities	$ 124,739	$ 124,731
Interest rate on notes (as a percent)	3.60%	3.60%
Senior unsecured notes 3.6%, due in 2026
Long-Term Obligations
Long-term obligations gross including current maturities	$ 125,000	$ 125,000
Deferred Finance Costs, Net, Total	261	269
Long-term obligations including current maturities	$ 124,739	$ 124,731
Interest rate on notes (as a percent)	3.60%	3.60%
Capital lease obligations
Long-Term Obligations
Long-term obligations gross including current maturities	$ 1,325	$ 1,542
Long-term obligations including current maturities	$ 1,325	$ 1,542