Derivative Instruments (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Change in fair value of derivatives:
Net realized investment gains (losses)	$ (205)	[1]	$ 14	[1]
Change in fair value of embedded derivatives:
Net realized investment gains (losses)	$ 439		$ (12)

[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.