Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Available-for-sale debt securities, amortized cost (in dollars)	$ 1,398,533	$ 1,199,409
Equity securities, amortized cost	$ 73,244	$ 77,512
Common stock, par value (in dollars per share)	$ 0.0002	$ 0.0002
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	30,424,391	29,988,460
Common stock, shares outstanding	30,424,391	29,988,460
Preferred stock par value (in dollars per share)	$ 0.00125	$ 0.00125
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0