Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Debt securities, Amortized cost	$ 235,830	$ 167,231
Available-for-sale Equity securities, Amortized cost	53,132	47,750
Trading equity securities, cost	$ 953	$ 0
Preferred stock, no par value
Preferred stock, authorized	18,100,000	18,100,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, no par value
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	8,762,416	9,662,761
Common stock, outstanding	8,762,416	9,662,761
7% Series A Cumulative Convertible Preferred Stock [Member]
Preferred stock, no par value
Preferred stock, authorized	1,500,000	1,500,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Series B Preferred Stock [Member]
Preferred stock, no par value
Preferred stock, authorized	400,000	400,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0