Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 12,437	$ 8,355	$ 21,309
Adjustments for changes in:
Foreign exchange translation	1,820	3,193	653
Unrecognized employee benefit costs	28,678	(10,520)	(23,028)
Unrealized holding gains (losses) on marketable securities	431	149	(28)
Fair value of cash flow hedges	(251)	102	(707)
Reclassification adjustments for items included in net income:
Amortization of unrecognized employee benefit costs	5,643	3,962	3,664
Realized (gains) losses from sale of marketable securities	(57)	(78)	13
Realized (gains) losses from settlement of cash flow hedges	246	107	(383)
Other comprehensive income (loss)	36,510	(3,085)	(19,816)
Comprehensive income	$ 48,947	$ 5,270	$ 1,493