DEBT, CREDIT FACILITY, AND CAPITAL LEASE OBLIGATIONS (Long-term Debt) (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total Long-Term Debt	$ 1,629,000	$ 1,466,000
Less Unamortized Discount and Debt Issuance Costs	14,000	12,000
Current Maturities of Long-Term Debt	0	100,000
Total Long-Term Debt, Net	$ 1,615,252	1,354,423
2011 Notes \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	5.15%
Total Long-Term Debt	$ 250,000	250,000
2012 Notes \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	3.85%
Total Long-Term Debt	$ 150,000	150,000
2014 Notes \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	5.00%
Total Long-Term Debt	$ 150,000	150,000
2015 Notes \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	3.05%
Total Long-Term Debt	$ 300,000	300,000
2018 Notes \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	4.85%
Total Long-Term Debt	$ 300,000	0
2010 Pima A \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	5.25%
Total Long-Term Debt	$ 100,000	100,000
2012 Pima A \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	4.50%
Total Long-Term Debt	$ 16,000	16,000
2013 Pima A \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	4.00%
Total Long-Term Debt	$ 91,000	91,000
2013 Apache A \| Unsecured Debt
Debt Instrument [Line Items]
Effective interest rate (in percentage)	2.42%
Total Long-Term Debt	$ 0	100,000
2009 Pima A \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	4.95%
Total Long-Term Debt	$ 80,000	80,000
2009 Coconino A \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	5.13%
Total Long-Term Debt	$ 15,000	15,000
2010 Coconino A \| Secured Debt
Debt Instrument [Line Items]
Effective interest rate (in percentage)	2.34%
Total Long-Term Debt	$ 0	37,000
2012 Apache A \| Unsecured Debt
Debt Instrument [Line Items]
Interest Rate (in percentage)	4.50%
Total Long-Term Debt	$ 177,000	$ 177,000

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 210
-Section S99
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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6036836-161870

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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