Investments, Investment Results (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investment income [Abstract]
Interest on debt securities	$ 1,755	$ 1,328	$ 4,713	$ 3,432
Dividends on equity securities	147	121	381	324
Interest on cash and cash equivalents	5	1	60	2
Total investment income	1,907	1,450	5,154	3,758
Proceeds from sales and maturity of marketable securities	$ 42,500	$ 21,800	$ 134,918	$ 65,869