Investments (Trading Account Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading account assets, at amortized cost or cost	$ 154,520	$ 154,608
Trading account assets, at fair value	158,202	149,871
Fixed maturities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading account assets, at amortized cost or cost	147,102	147,057
Trading account assets, at fair value	147,075	139,513
Equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading account assets, at amortized cost or cost	7,418	7,551
Trading account assets, at fair value	$ 11,127	$ 10,358