Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 133,306	$ 125,096	$ 111,764
OTHER COMPREHENSIVE INCOME (LOSS):
Translation adjustments, net of tax	(80)	(70)	(32)
Actuarial gain (loss) on defined benefit pension plans, net of tax	(76)	87	0
Total other comprehensive income (loss)	(156)	17	(32)
COMPREHENSIVE INCOME	$ 133,150	$ 125,113	$ 111,732