Fair Value Measurements - Contractual Maturities of Available For Sale Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Maturing in one year or less	$ 1,270	$ 774
Maturing in second year through fifth year	16,979	13,852
Maturing in sixth year through tenth year	41,323	36,273
Maturing after ten years	19,347	18,597
Total debt securities	$ 78,919	$ 69,496