Consolidated Statements of Comprehensive Income (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	$ 7,283	$ 5,886	$ 3,700	$ 3,337
Unrealized losses on marketable securities, net of tax	(13)	(43)	(24)	(47)
Comprehensive income	$ 7,270	$ 5,843	$ 3,676	$ 3,290