CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement Of Income and Comprehensive Income [Abstract]
Net income	$ 63,283	$ 40,416	$ 102,671	$ 75,492
Other comprehensive income (loss):
Pension adjustment and reclassification adjustment, net of taxes	84	124	168	248
Foreign currency translation	467	(383)	(4)	(627)
Unrealized gain (loss) on securities, net of taxes	38	30	2	(31)
Comprehensive income	$ 63,872	$ 40,187	$ 102,837	$ 75,082