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	$ 53,291	$ 44,478	$ 42,160
Other comprehensive income (loss), net of tax
Change in foreign currency translation adjustment	(1,688)	(150)	(26)
Change in retirement liabilities, net of tax benefit (expense) of $2,474, $(691), and $(2,647) for 2011, 2010, and 2009, respectively	(3,853)	1,072	4,047
Other comprehensive (loss) income	(5,541)	922	4,021
Comprehensive income	$ 47,750	$ 45,400	$ 46,181