Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Securities, fair value	$ 462,880	$ 470,006
Common stock, par value	$ 1.00	$ 1.00
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	32,731,215	31,894,563
Common stock, shares outstanding	32,731,215	31,894,563
Accumulated other comprehensive loss, tax expense (benefit)	$ (1,243)	$ (795)
Senior Preferred Stock [Member]
Preferred stock, par value	$ 1.00	$ 1.00
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Cumulative Preferred Stock [Member]
Preferred stock, par value	$ 5.00	$ 5.00
Preferred stock, shares authorized	900,000	900,000
Preferred stock, shares issued	0	0