FAIR VALUE OF FINANCIAL INSTRUMENTS (Debt) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Feb. 26, 2013	Dec. 31, 2012
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	$ 947,982		$ 880,215
Estimated Fair Value	953,389		901,893
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		286,800
Estimated Fair Value	0		286,800
5.74% Senior notes due 2013 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	125,003		125,011
Estimated Fair Value	126,090		128,198
Interest rate	5.74%
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	163,096		168,491
Interest rate	5.51%
3.84% Senior notes due 2021 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	99,072		100,677
Estimated Fair Value	99,072		100,677
Interest rate	3.84%
3.70% Senior notes due 2023 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	225,000		0
Estimated Fair Value	216,224		0
Interest rate	3.70%	3.70%
3.85% Senior notes due 2025 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	91,478		0
Estimated Fair Value	91,478		0
Interest rate	3.85%	3.85%
4.24% Senior notes due 2026 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	180,518		198,581
Estimated Fair Value	180,518		198,581
Interest rate	4.24%
4.05% Senior notes due 2028 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	67,359		0
Estimated Fair Value	67,359		0
Interest rate	4.05%	4.05%
Other debt [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Carrying Value	1,152		10,746
Estimated Fair Value	$ 1,152		$ 10,746