DEBT (Narrative) (Details)	1 Months Ended			3 Months Ended
	Mar. 31, 2018 USD ($)	Feb. 28, 2018 USD ($)	Jan. 31, 2018 USD ($)	Mar. 31, 2019 USD ($) item	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Discounts and debt issuance costs				$ 1,239,000	$ 1,473,000
Total long-term debt - face value	$ 2,846,412,000			2,846,390,000	2,846,412,000	$ 2,846,396,000
Long term debt	2,775,709,000			2,780,613,000	2,775,709,000	2,779,380,000
Repayments of long term debt				$ 6,000	892,038,000
Net proceeds		$ 846,029,000
Net noncash expense					466,000
Premium for repayments of debt					5,608,000
Transaction costs for repayments of debt					1,314,000
Combined charge, component of interest expense					7,388,000
Investment-Grade Type Covenants Governed [Member]
Debt Instrument [Line Items]
Number of indentures with customary investment-grade type covenants | item				3
7.50% notes due 2021 [Member]
Debt Instrument [Line Items]
Maturity year				2021
Bank Line of Credit [Member]
Debt Instrument [Line Items]
Maturity date				Dec. 01, 2021
Maximum borrowing capacity				$ 750,000,000
Commitment fee				0.15%
Available borrowing capacity				$ 516,970,000
Borrowings				$ 178,500,000
Bank Line of Credit [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Applicable margin on borrowing rate				1.25%
Bank Line of Credit [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Applicable margin on borrowing rate				0.25%
Bank Line of Credit [Member] | Maximum, Upon Certain Acquisitions [Member]
Debt Instrument [Line Items]
Debt to EBITDA ratio				3.75
Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Outstanding standby letters of credit				$ 54,530,000
Period of standby letters of credit				1 year
Standby Letters of Credit [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Applicable margin on borrowing rate				0.175%
Maximum [Member] | Bank Line of Credit [Member]
Debt Instrument [Line Items]
Debt to EBITDA ratio				3.5
Commitment fee				0.25%
Maximum [Member] | Bank Line of Credit [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Applicable margin on borrowing rate				1.75%
Maximum [Member] | Bank Line of Credit [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Applicable margin on borrowing rate				0.75%
Minimum [Member] | Bank Line of Credit [Member]
Debt Instrument [Line Items]
EBITDA to net cash interest expense ratio				3.0
Commitment fee				0.10%
Minimum [Member] | Bank Line of Credit [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Applicable margin on borrowing rate				1.00%
Minimum [Member] | Bank Line of Credit [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Applicable margin on borrowing rate				0.00%
Notes [Member] | Investment-Grade Type Covenants Governed [Member]
Debt Instrument [Line Items]
Total long-term debt - face value				$ 2,846,188,000
Notes [Member] | Floating-Rate Notes Due 2020 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value	250,000,000			$ 250,000,000	250,000,000	250,000,000
Maturity year				2020
Notes [Member] | 7.50% notes due 2021 [Member]
Debt Instrument [Line Items]
Face value			$ 35,111,000
Net noncash expense			263,000
Repayments of debt			40,719,000
Premium for repayments of debt			$ 5,608,000
Notes [Member] | 4.70% notes due 2048 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value	460,949,000			$ 460,949,000	460,949,000	$ 460,949,000
Maturity year				2048
Face value	460,949,000	$ 350,000,000			460,949,000
Interest rate		4.70%		4.70%		4.70%
Net noncash expense		$ 203,000
Premium for repayments of debt	38,164,000
Notes [Member] | Floating-Rate Notes Due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value	500,000,000			$ 500,000,000	500,000,000	$ 500,000,000
Maturity year				2021
Face value		$ 500,000,000
Notes [Member] | 7.15% notes due 2037 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value	129,239,000			$ 129,239,000	$ 129,239,000	$ 129,239,000	$ 240,188,000
Maturity year				2037
Repayments of long term debt	$ 110,949,000
Interest rate	7.15%			7.15%	7.15%
Transaction costs for repayments of debt	$ 1,314,000