Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net earnings	$ 17,249	$ 13,777	$ 25,296	$ 42,131
Unrealized (loss) gain on short-term investments	(165)	61	(126)	23
Changes in pension plan assets and benefit obligations	(1)		9	(10)
Tax effect of preceding losses, gains or changes	64	(24)	45	(5)
Total comprehensive income	$ 17,147	$ 13,814	$ 25,224	$ 42,139