Investments, Investment Results (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investment income [Abstract]
Interest on debt securities	$ 1,616	$ 1,209	$ 2,959	$ 2,104
Dividends on equity securities	128	92	234	203
Interest on cash and cash equivalents	(43)	1	55	1
Total investment income	1,701	1,302	3,248	2,308
Net realized gains	913	2,056	2,617	3,388
Proceeds from sales and maturity of marketable securities	$ 36,100	$ 23,100	$ 92,411	$ 44,081