Investments - Contractual Maturities of Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Amortized Cost
Due in one year or less	$ 113,393
Due after one year through five years	98,130
Due after ten years through fifteen years	99
Amortized Cost	211,622
Preferred stock	22,930
Restricted investments	5,640
Amortized Cost	240,192	$ 199,429
Fair Value
Due in one year or less	113,944
Due after one year through five years	99,398
Due after ten years through fifteen years	82
Fair Value	213,424
Preferred stock	23,232
Restricted investments	5,640
Fair Value	$ 242,296	$ 198,312