DEBT (Debt) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2018		Feb. 28, 2018	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017	Mar. 31, 2017
Debt Instrument [Line Items]
Total short-term debt		$ 200,000			$ 0		$ 0
Total long-term debt - face value		2,846,402			2,881,529		2,846,541
Unamortized discounts and debt issuance costs		(68,250)			(26,664)		(31,748)
Total long-term debt - book value		2,778,152			2,854,865		2,814,793
Less current maturities		23			41,383		4,827
Total long-term debt - reported value		2,778,129			2,813,482		2,809,966
Estimated fair value of long-term debt		2,743,429			2,983,419		3,068,236
Bank Line of Credit [Member]
Debt Instrument [Line Items]
Total short-term debt	[1],[2]	$ 200,000			0		0
Maturity date		Dec. 31, 2021
Effective interest rate	[1],[2]	1.25%
Bank Line of Credit [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 0	[1]		250,000	[1]	0	[1]		$ 235,000
Maturity date		Dec. 31, 2021
Term Loan Due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value	[3]	$ 0			350,000		0
Maturity year		2018
Notes [Member] | Floating-Rate Notes Due 2020 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 250,000			250,000		250,000
Maturity year		2020
Effective interest rate		3.21%
Notes [Member] | Floating-Rate Notes Due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 500,000			0		600,000
Maturity year		2021
Effective interest rate		3.23%
Notes [Member] | 7.50% notes due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 0			35,111		0
Interest rate		7.50%
Maturity year		2021
Notes [Member] | 8.85% notes due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 6,000			6,000		6,000
Interest rate		8.85%
Maturity year		2021
Effective interest rate		8.88%
Notes [Member] | Term loan due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 0			250,000		250,000		$ 250,000
Maturity year		2021
Notes [Member] | 4.50% notes due 2025 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 400,000			400,000		400,000
Interest rate		4.50%
Maturity year		2025
Effective interest rate		4.65%
Notes [Member] | 3.90% notes due 2027 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 400,000			400,000		400,000
Interest rate		3.90%							3.90%	3.90%
Maturity year		2027
Effective interest rate		4.00%
Notes [Member] | 7.15% notes due 2037 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 129,239			$ 240,188		240,188
Interest rate		7.15%			7.15%
Maturity year		2037
Effective interest rate		8.05%
Notes [Member] | 4.50% notes due 2047 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 700,000			$ 700,000		700,000
Interest rate		4.50%							4.50%
Maturity year		2047
Effective interest rate		4.59%
Notes [Member] | 4.70% notes due 2048 [Member]
Debt Instrument [Line Items]
Total long-term debt - face value		$ 460,949			0		0
Interest rate		4.70%		4.70%
Maturity year		2048
Effective interest rate		5.42%
Other Notes [Member]
Debt Instrument [Line Items]
Total long-term debt - face value	[3]	$ 214			$ 230		$ 353
Effective interest rate	[3]	6.46%

[1] 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.

[2] Reflects the margin above LIBOR for LIBOR-based borrowings; we also paid upfront fees that are amortized to interest expense and pay fees for unused borrowing capacity and standby letters of credit.

[3] 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