Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Tax (provision)/benefit of marketable securities unrealized gain	$ 2,456		$ 7,851
Tax (provision)/ benefit of foreign currency translation gain		$ 1,365		$ 1,710