Fair Value Measurements - Contractual Maturities of Available For Sale Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Maturing in one year or less	$ 2,587	$ 774
Maturing in second year through fifth year	18,411	13,852
Maturing in sixth year through tenth year	40,748	36,273
Maturing after ten years	18,877	18,597
Total debt securities	$ 80,623	$ 69,496