DEBT (Narrative) (Details)		1 Months Ended									3 Months Ended	6 Months Ended				12 Months Ended
		Mar. 31, 2018 USD ($)	Feb. 28, 2018 USD ($)	Jan. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)		Jul. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)		Mar. 31, 2017 USD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2018 USD ($) item		Jun. 30, 2017 USD ($)		Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Discounts and debt issuance costs												$ 2,698,000
Total long-term debt - face value					$ 2,881,529,000			$ 3,369,058,000				2,846,407,000		$ 3,369,058,000		$ 2,881,529,000
Repayments of long term debt							$ 565,560,000					892,044,000		235,007,000
Proceeds from issuance of long-term debt												850,000,000		1,600,000,000
Net proceeds			$ 846,029,000
Net noncash expense							3,029,000				$ 466,000					7,257,000
Premium for repayments of debt							43,020,000				5,608,000					139,187,000
Transaction costs for repayments of debt							$ 28,000				1,314,000					1,586,000
Combined charge, component of interest expense											7,388,000					148,030,000
Total short-term debt					0			0				$ 360,000,000		0		0
Investment-Grade Type Covenants Governed [Member]
Debt Instrument [Line Items]
Number of indentures with customary investment-grade type covenants | item												3
Bank Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity												$ 750,000,000
Commitment fee												0.15%
Available borrowing capacity												$ 344,933,000
Borrowings												$ 360,000,000
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												$ 45,067,000
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%
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%
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%
Term Loan Due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value	[1]				350,000,000			0				$ 0		0		350,000,000
Maturity year												2018
Debt issued, term												6 months
Notes [Member]
Debt Instrument [Line Items]
Face value								1,000,000,000						1,000,000,000
Net proceeds								989,512,000
Notes [Member] | 3.90% notes due 2027 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value					400,000,000			400,000,000				$ 400,000,000		400,000,000		400,000,000
Maturity year												2027
Face value								$ 400,000,000						$ 400,000,000
Interest rate								3.90%		3.90%		3.90%		3.90%
Net proceeds										$ 345,450,000
Notes [Member] | 3.90% notes due 2027 [Member] | June 2017 Issuance [Member]
Debt Instrument [Line Items]
Face value								$ 50,000,000						$ 50,000,000
Notes [Member] | 3.90% notes due 2027 [Member] | March 2017 Issuance [Member]
Debt Instrument [Line Items]
Face value										350,000,000
Notes [Member] | Term loan due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value	[1]				250,000,000			250,000,000				$ 0		250,000,000		250,000,000
Maturity year												2021
Notes [Member] | Investment-Grade Type Covenants Governed [Member]
Debt Instrument [Line Items]
Total long-term debt - face value												$ 2,846,188,000
Notes [Member] | 4.50% notes due 2047 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value					700,000,000			700,000,000				$ 700,000,000		700,000,000		700,000,000
Maturity year												2047
Face value								$ 700,000,000						$ 700,000,000
Interest rate								4.50%				4.50%		4.50%
Notes [Member] | 4.50% notes due 2025 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value					400,000,000			$ 400,000,000				$ 400,000,000		$ 400,000,000		400,000,000
Maturity year												2025
Interest rate												4.50%
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		250,000,000
Maturity year												2020
Face value								250,000,000						250,000,000
Notes [Member] | 10.375% notes due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value					0			250,000,000				$ 0		250,000,000		0
Maturity year												2018
Interest rate												10.375%
Notes [Member] | 7.00% notes due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value					0			272,512,000				$ 0		272,512,000		0
Maturity year												2018
Interest rate												7.00%
Notes [Member] | 7.50% notes due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value					35,111,000			600,000,000				$ 0		600,000,000		35,111,000
Maturity year												2021
Face value				$ 35,111,000	564,889,000											564,889,000
Interest rate												7.50%
Net noncash expense				263,000	4,228,000
Repayments of debt				40,719,000	662,613,000
Premium for repayments of debt				$ 5,608,000	96,167,000
Transaction costs for repayments of debt					1,558,000
Notes [Member] | 4.70% notes due 2048 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value					0			0				$ 460,949,000		0		0
Maturity year												2048
Face value		$ 460,949,000	$ 350,000,000								$ 460,949,000
Interest rate			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					0			0				$ 500,000,000		0		0
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					$ 240,188,000			240,188,000				$ 129,239,000		240,188,000		$ 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
Bank Line of Credit [Member]
Debt Instrument [Line Items]
Maturity date												Dec. 31, 2021
Total long-term debt - face value					$ 250,000,000	[2]		$ 0	[2]	$ 235,000,000		$ 0	[2]	$ 0	[2]	$ 250,000,000	[2]

[1] This short-term loan was refinanced on a long-term basis in February 2018 as discussed below. Thus, it was classified as long-term debt as of December 31, 2017

[2] Borrowings on the bank line of credit are classified as short-term debt if we intend to repay within twelve months and as long-term debt otherwise.