CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short term investments:
Unrealized (loss) gain on short term investments, income tax (benefit) expense	$ (8)	$ (2)	$ 4
Short term investments, reclassification adjustments, income tax expense			$ 2