Investments (Summary of Realized Gain (Loss) on Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule of Investments [Line Items]
(Loss) gain on investments	$ (10)	$ 410	$ 2,491	$ 484
Change in unrealized gain on other investments	(62)		(503)
Other-than-temporary impairment	(3,407)	(2,587)	(3,407)	(2,888)
Net realized (losses) gains	(3,479)	(2,177)	(1,419)	(2,404)
Us Treasury Securities and Obligations of U.S. Government [Member]
Schedule of Investments [Line Items]
(Loss) gain on investments
Corporate Bonds [Member]
Schedule of Investments [Line Items]
(Loss) gain on investments	(148)		(18)	80
Collateralized Corporate Bank Loans [Member]
Schedule of Investments [Line Items]
(Loss) gain on investments	20	(36)	48	(18)
Municipal Bonds [Member]
Schedule of Investments [Line Items]
(Loss) gain on investments	101	(44)	84	(68)
Equity Securities [Member]
Schedule of Investments [Line Items]
(Loss) gain on investments	$ 17	$ 490	$ 2,377	$ 490