Derivative Instruments (Details 1) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in fair value of derivatives:
Net realized investment gains (losses)	[1]	$ 4,024	$ (1,483)	$ 995
Change in fair value of embedded derivatives:
Net realized investment gains (losses)		$ (5,076)	$ 2,529	$ (1,157)

[1] Includes the gains or losses recognized at the expiration of the option term or early termination and the changes in fair value for open options.