FAIR VALUE OF FINANCIAL INSTRUMENTS (Debt) (Detail) (USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
5.51% Senior notes due 2017 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Interest rate | 5.51% | ' |
3.84% Senior notes due 2021 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Interest rate | 3.84% | ' |
3.70% Senior notes due 2023 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Interest rate | 3.70% | ' |
3.85% Senior notes due 2025 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Interest rate | 3.85% | ' |
4.24% Senior notes due 2026 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Interest rate | 4.24% | ' |
4.05% Senior notes due 2028 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Interest rate | 4.05% | ' |
4.11% Senior Notes [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Interest rate | 4.11% | ' |
Reported Value Measurement [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | $972,035 | $959,938 |
Reported Value Measurement [Member] | Industrial revenue bond, due 2023 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 8,400 | 8,400 |
Reported Value Measurement [Member] | Revolving credit agreement, due 2017 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 50,000 | 50,000 |
Reported Value Measurement [Member] | 5.51% Senior notes due 2017 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 150,000 | 150,000 |
Reported Value Measurement [Member] | 3.84% Senior notes due 2021 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 99,027 | 98,632 |
Reported Value Measurement [Member] | 3.70% Senior notes due 2023 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 225,000 | 225,000 |
Reported Value Measurement [Member] | 3.85% Senior notes due 2025 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 91,564 | 88,555 |
Reported Value Measurement [Member] | 4.24% Senior notes due 2026 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 180,096 | 173,557 |
Reported Value Measurement [Member] | 4.05% Senior notes due 2028 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 67,243 | 64,411 |
Reported Value Measurement [Member] | 4.11% Senior Notes [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 100,000 | 100,000 |
Reported Value Measurement [Member] | Other debt [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Carrying Value | 705 | 1,383 |
Estimate of Fair Value Measurement [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 969,875 | 946,389 |
Estimate of Fair Value Measurement [Member] | Industrial revenue bond, due 2023 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 8,400 | 8,400 |
Estimate of Fair Value Measurement [Member] | Revolving credit agreement, due 2017 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 50,000 | 50,000 |
Estimate of Fair Value Measurement [Member] | 5.51% Senior notes due 2017 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 163,324 | 163,059 |
Estimate of Fair Value Measurement [Member] | 3.84% Senior notes due 2021 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 99,027 | 98,632 |
Estimate of Fair Value Measurement [Member] | 3.70% Senior notes due 2023 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 216,947 | 209,140 |
Estimate of Fair Value Measurement [Member] | 3.85% Senior notes due 2025 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 91,564 | 88,555 |
Estimate of Fair Value Measurement [Member] | 4.24% Senior notes due 2026 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 180,096 | 173,557 |
Estimate of Fair Value Measurement [Member] | 4.05% Senior notes due 2028 [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 67,243 | 64,411 |
Estimate of Fair Value Measurement [Member] | 4.11% Senior Notes [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | 92,569 | 89,252 |
Estimate of Fair Value Measurement [Member] | Other debt [Member] | ' | ' |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ' | ' |
Estimated Fair Value | $705 | $1,383 |