CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net Income	$ 144,595	$ 152,624	$ 99,365
Other Comprehensive Income:
Reclassification of loss on derivative instruments from other comprehensive income to net income, net of tax	1,591	1,319	1,657
Pension and postretirement benefit plans, net of tax:
Net actuarial (loss) gain arising during the year	(10,627)	(1,376)	2,190
Less reclassification of amounts from other comprehensive income to net income:
Amortization of prior service credit	(2,330)	(2,327)	(2,368)
Amortization of net actuarial loss	3,371	3,361	5,989
Pension and postretirement benefit plans, net of tax	(9,586)	(342)	5,811
Unrealized holding gains on securities arising during the year, net of tax	165	13	0
Unrealized foreign currency translation adjustment	(1,559)	1,816	4,668
Other Comprehensive (Loss) Income, Net Of Tax	(9,389)	2,806	12,136
Comprehensive Income	135,206	155,430	111,501
Related Tax Benefit (Expense) of Other Comprehensive (Loss) Income Included in Above Amounts:
Reclassification of loss on derivative instruments from other comprehensive income to net income	(951)	(770)	(967)
Pension and postretirement benefit plans:
Net actuarial (loss) gain arising during the year	6,442	837	(1,348)
Less reclassification of amounts from other comprehensive income to net income:
Amortization of prior service credit	1,413	1,416	1,447
Amortization of net actuarial loss	(2,044)	(2,045)	(3,584)
Pension and postretirement benefit plans	5,811	208	(3,485)
Unrealized holding gains on securities arising during the year	(65)	(6)	0
Total Net Tax Benefit (Expense) Included In Other Comprehensive (Loss) Income	$ 4,795	$ (568)	$ (4,452)