CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net income	$ 40,368	$ 40,020	$ 32,572
Other comprehensive income:
Change in unrecognized pension and post- retirement benefit costs	(157)	(2,687)	(322)
Tax expense (benefit) on change in unrecognized pension and post-retirement benefit costs	(10)	976	98
Foreign currency translation adjustments	(626)	(5,723)	3,756
Tax expense (benefit) on foreign currency translation adjustments	454	229	(37)
Other comprehensive income (loss)	(339)	(7,205)	3,495
Comprehensive income (loss) attributable to non-controlling interest	15	(93)	100
Comprehensive income attributable to controlling interest	$ 40,044	$ 32,722	$ 36,167