Investments (Details 3) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Continuous unrealized loss position, Fair Value
Fair Value, Total	$ 111,978	$ 105,560
Continuous unrealized loss position, Gross Unrealized Loss
Gross Unrealized Loss, Total	(186)	(147)
Government-sponsored enterprises
Continuous unrealized loss position, Fair Value
Less than one year, Fair value	48,138	15,293
Fair Value, Total	48,138	15,293
Continuous unrealized loss position, Gross Unrealized Loss
Less than one year, Gross Unrealized Loss	(119)	(39)
Gross Unrealized Loss, Total	(119)	(39)
Corporate notes and bonds
Continuous unrealized loss position, Fair Value
Less than one year, Fair value	63,840	86,824
Greater than one year, Fair value		3,443
Fair Value, Total	63,840	90,267
Continuous unrealized loss position, Gross Unrealized Loss
Less than one year, Gross Unrealized Loss	(67)	(97)
Greater than one year, Gross Unrealized Loss		(11)
Gross Unrealized Loss, Total	$ (67)	$ (108)