Investments (Trading Account Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Investment [Line Items]
Trading account assets, at fair value	$ 38,956	$ 35,328
Trading account assets, at amortized cost or cost	35,489	35,484
Fixed maturities
Investment [Line Items]
Trading account assets, at fair value	21,649	19,558
Trading account assets, at amortized cost or cost	23,560	23,555
Equity securities
Investment [Line Items]
Trading account assets, at fair value	17,307	15,770
Trading account assets, at amortized cost or cost	$ 11,929	$ 11,929