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 Income and Comprehensive Income [Abstract]
Net income	$ 64,885	$ 53,760	$ 167,556	$ 129,252
Other comprehensive income (loss):
Pension adjustment and reclassification adjustment, net of taxes	85	125	253	372
Foreign currency translation	(649)	214	(653)	(413)
Unrealized gain (loss) on securities, net of taxes	(38)	28	(36)	(2)
Comprehensive income	$ 64,283	$ 54,127	$ 167,120	$ 129,209