DEBT (Narrative) (Details)		1 Months Ended										3 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 ($)		Mar. 31, 2018 USD ($) item		Mar. 31, 2017 USD ($)		Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Discounts and debt issuance costs												$ 1,473,000
Total long-term debt - face value		$ 2,846,412,000				$ 2,881,529,000				$ 2,354,064,000		2,846,412,000		$ 2,354,064,000		$ 2,881,529,000
Long term debt		2,775,709,000				2,854,865,000				2,329,387,000		2,775,709,000		2,329,387,000		2,854,865,000
Repayments of long term debt								$ 565,560,000				892,038,000		5,000
Proceeds from issuance of long-term debt												850,000,000		350,000,000
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		200,000,000				0				0		$ 200,000,000		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										$ 750,000,000
Commitment fee												0.15%
Available borrowing capacity		506,761,000										$ 506,761,000
Borrowings		0										$ 0
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		43,239,000										$ 43,239,000
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],[2]	0				350,000,000				0		$ 0		0		350,000,000
Long term debt						350,000,000										350,000,000
Maturity year												2018
Debt issued, term												6 months
Notes [Member]
Debt Instrument [Line Items]
Face value									$ 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				$ 350,000,000		$ 400,000,000		$ 350,000,000		400,000,000
Maturity year												2027
Face value									$ 400,000,000
Interest rate		3.90%							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
Notes [Member] | 3.90% notes due 2027 [Member] | March 2017 Issuance [Member]
Debt Instrument [Line Items]
Face value										350,000,000				$ 350,000,000
Notes [Member] | Delayed draw term loan [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 0	[1]			250,000,000	[1]		250,000,000	0	[1]	$ 0	[1]	0	[1]	250,000,000	[1]
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										$ 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				0		$ 700,000,000		0		700,000,000
Maturity year												2047
Face value									$ 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		400,000,000
Maturity year												2025
Interest rate		4.50%										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				0		$ 250,000,000		0		250,000,000
Maturity year												2020
Face value									$ 250,000,000
Notes [Member] | 10.375% notes due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 0				0				250,000,000		$ 0		250,000,000		0
Maturity year												2018
Interest rate		10.375%										10.375%
Notes [Member] | 7.00% notes due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 0				0				272,512,000		$ 0		272,512,000		0
Maturity year												2018
Interest rate		7.00%										7.00%
Notes [Member] | 7.50% notes due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 0				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%										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% Percent due 2048 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 460,949,000				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%								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				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		129,239,000				$ 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%				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		$ 0	[1],[3]			$ 250,000,000	[1],[3]		$ 235,000,000	$ 235,000,000	[1],[3]	$ 0	[1],[3]	$ 235,000,000	[1],[3]	$ 250,000,000	[1],[3]

[1] Non-publicly traded debt.

[2] 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

[3] 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.