FAIR VALUE OF FINANCIAL INSTRUMENTS (Debt) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	$ 936,612	$ 959,938
Estimated Fair Value	950,196	946,389
Industrial revenue bond, due 2023 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	8,400	8,400
Estimated Fair Value	8,400	8,400
Revolving credit agreement, due 2017 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	0	50,000
Estimated Fair Value	0	50,000
5.51% Senior notes due 2017 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	150,000	150,000
Estimated Fair Value	164,382	163,059
Debt Instrument, Interest Rate, Stated Percentage	5.51%
3.84% Senior notes due 2021 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	99,431	98,632
Estimated Fair Value	99,431	98,632
Debt Instrument, Interest Rate, Stated Percentage	3.84%
3.70% Senior notes due 2023 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	225,000	225,000
Estimated Fair Value	225,490	209,140
Debt Instrument, Interest Rate, Stated Percentage	3.70%
3.85% Senior notes due 2025 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	94,771	88,555
Estimated Fair Value	94,771	88,555
Debt Instrument, Interest Rate, Stated Percentage	3.85%
4.24% Senior notes due 2026 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	187,924	173,557
Estimated Fair Value	187,924	173,557
Debt Instrument, Interest Rate, Stated Percentage	4.24%
4.05% Senior notes due 2028 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	70,479	64,411
Estimated Fair Value	70,479	64,411
Debt Instrument, Interest Rate, Stated Percentage	4.05%
4.11% Senior Notes [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	100,000	100,000
Estimated Fair Value	98,712	89,252
Debt Instrument, Interest Rate, Stated Percentage	4.11%
Other debt [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	607	1,383
Estimated Fair Value	$ 607	$ 1,383