Investments (Summary of Realized Gain (Loss) on Investments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Schedule of Investments [Line Items]
Gain (loss) on investments	$ 4,141	$ (15)
Other-than-temporary impairment	0
Gain (Loss) on Investments, Total	11,937	(4,835)
Other Investments [Member]
Schedule of Investments [Line Items]
Unrealized gain on investment	36
Unrealized loss on investment		(363)
U.S. Treasury Securities and Obligations of U.S. Government [Member]
Schedule of Investments [Line Items]
Gain (loss) on investments
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Gain (loss) on investments	23	(8)
Collateralized Corporate Bank Loans [Member]
Schedule of Investments [Line Items]
Gain (loss) on investments	17	12
Municipal Bonds [Member]
Schedule of Investments [Line Items]
Gain (loss) on investments	4,101	(21)
Mortgage Backed [Member]
Schedule of Investments [Line Items]
Gain (loss) on investments		2
Equity Securities [Member]
Schedule of Investments [Line Items]
Unrealized gain on investment	$ 7,760
Unrealized loss on investment		$ (4,457)