Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Series A 3% Preferred Stock [Member]	Series B-1 8.48% Preferred Stock [Member]	Preferred Equity [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Series A 3% Preferred Stock [Member]	Retained Earnings [Member] Series B-1 8.48% Preferred Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2017	$ 381,177			$ 17,329	$ 161	$ 121,058	$ 257,078			$ (11,916)	$ (2,533)
Comprehensive income:
Net income	9,288						9,288
Other comprehensive income (loss), net of tax	(6,247)									(6,247)
Purchases of common stock for treasury	(113)										(113)
Share-based compensation plans:
Share-based compensation	302					302
Stock options exercised	76					(1)					77
Restricted stock awards forfeited						446					(446)
Cash dividends declared:
Preferred stock dividends per share		$ (1)	$ (364)					$ (1)	$ (364)
Common stock dividends per share	(3,816)						(3,816)
Balance at Mar. 31, 2018	380,302			17,329	161	121,805	262,185			(18,163)	(3,015)
Balance at Dec. 31, 2017	381,177			17,329	161	121,058	257,078			(11,916)	(2,533)
Comprehensive income:
Net income	32,035
Other comprehensive income (loss), net of tax	(9,904)									(9,904)
Balance at Sep. 30, 2018	392,154			17,329	161	122,478	276,563			(21,820)	(2,557)
Balance at Mar. 31, 2018	380,302			17,329	161	121,805	262,185			(18,163)	(3,015)
Comprehensive income:
Net income	12,170						12,170
Other comprehensive income (loss), net of tax	(2,133)									(2,133)
Share-based compensation plans:
Share-based compensation	457					457
Stock options exercised	233					(14)					247
Restricted stock awards issued						(143)					143
Stock awards	92					39					53
Cash dividends declared:
Preferred stock dividends per share		(1)	(365)					(1)	(365)
Common stock dividends per share	(3,818)						(3,818)
Balance at Jun. 30, 2018	386,937			17,329	161	122,144	270,171			(20,296)	(2,572)
Comprehensive income:
Net income	10,577						10,577
Other comprehensive income (loss), net of tax	(1,524)									(1,524)
Share-based compensation plans:
Share-based compensation	338					338
Stock options exercised	11					(4)					15
Cash dividends declared:
Preferred stock dividends per share		(1)	(364)					(1)	(364)
Common stock dividends per share	(3,820)						(3,820)
Balance at Sep. 30, 2018	392,154			17,329	161	122,478	276,563			(21,820)	(2,557)
Balance at Dec. 31, 2018	396,293			17,328	161	122,704	279,867			(21,281)	(2,486)
Cumulative-effect adjustment at Dec. 31, 2018	(710)						(710)
Adjusted Balance at Dec. 31, 2018	395,583			17,328	161	122,704	279,157			(21,281)	(2,486)
Comprehensive income:
Net income	11,521						11,521
Other comprehensive income (loss), net of tax	5,510									5,510
Reclassification of income tax effects							2,783			(2,783)
Purchases of common stock for treasury	(193)										(193)
Share-based compensation plans:
Share-based compensation	182					182
Restricted stock units released						(362)					362
Cash dividends declared:
Preferred stock dividends per share		(1)	(364)					(1)	(364)
Common stock dividends per share	(3,985)						(3,985)
Balance at Mar. 31, 2019	408,253			17,328	161	122,524	289,111			(18,554)	(2,317)
Balance at Dec. 31, 2018	396,293			17,328	161	122,704	279,867			(21,281)	(2,486)
Cumulative-effect adjustment at Dec. 31, 2018	(710)						(710)
Adjusted Balance at Dec. 31, 2018	395,583			17,328	161	122,704	279,157			(21,281)	(2,486)
Comprehensive income:
Net income	35,755
Other comprehensive income (loss), net of tax	12,330									12,330
Balance at Sep. 30, 2019	432,617			17,328	161	124,322	304,622			(11,734)	(2,082)
Balance at Mar. 31, 2019	408,253			17,328	161	122,524	289,111			(18,554)	(2,317)
Comprehensive income:
Net income	11,401						11,401
Other comprehensive income (loss), net of tax	5,394									5,394
Common stock issued	1,151					1,151
Share-based compensation plans:
Share-based compensation	453					453
Restricted stock awards issued						(165)					165
Stock awards	63					17					46
Cash dividends declared:
Preferred stock dividends per share		(1)	(365)					(1)	(365)
Common stock dividends per share	(3,995)						(3,995)
Balance at Jun. 30, 2019	422,354			17,328	161	123,980	296,151			(13,160)	(2,106)
Comprehensive income:
Net income	12,833						12,833
Other comprehensive income (loss), net of tax	1,426									1,426
Purchases of common stock for treasury	(27)										(27)
Share-based compensation plans:
Share-based compensation	393					393
Restricted stock awards issued						(51)					51
Cash dividends declared:
Preferred stock dividends per share		$ (1)	$ (364)					$ (1)	$ (364)
Common stock dividends per share	(3,997)						(3,997)
Balance at Sep. 30, 2019	$ 432,617			$ 17,328	$ 161	$ 124,322	$ 304,622			$ (11,734)	$ (2,082)