Fair Value of Financial Instruments - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Fair Value of Financial Instruments (Textual) [Abstract]
Realized loss on impairment of securities			$ 1,874
Level 3
Fair Value of Financial Instruments (Textual) [Abstract]
Percentage of invested assets in total investment portfolio Level 3 recurring	3.30%		3.30%
Net realized investment losses	$ 2,587	$ 68	$ 6,133	$ 2,066