Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Legal Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2014		$ 176,000	$ 52,626	$ 539,311	$ 70,467	$ 181,152	$ (97,070)	$ 19,711
Stock-based compensation expense	$ 1,637			1,637
Stock-based compensation excess tax benefit recognized in income	0			0
Lapsed restricted stock units	(436)			(436)			641
Transfer from retained earnings/transfer to legal surplus					(32)	32
Net income	(2,504)					(2,504)
Cash dividends declared on common stock	(15,932)					(15,932)
Cash dividends declared on preferred stock	(13,862)					(13,862)
Stock purchased	8,950						(8,950)
Other comprehensive (loss) income, net of tax	(5,714)							(5,714)
Ending Balance at Dec. 31, 2015	897,077	176,000	52,626	540,512	70,435	148,886	(105,379)	13,997
Stock-based compensation expense	1,270			1,270
Stock-based compensation excess tax benefit recognized in income	0			0
Lapsed restricted stock units	(834)			(834)			519
Transfer from retained earnings/transfer to legal surplus					5,858	(5,858)
Net income	59,186					59,186
Cash dividends declared on common stock	(10,544)					(10,544)
Cash dividends declared on preferred stock	(13,862)					(13,862)
Stock purchased	0						0
Other comprehensive (loss) income, net of tax	(12,401)							(12,401)
Ending Balance at Dec. 31, 2016	920,411	176,000	52,626	540,948	76,293	177,808	(104,860)	1,596
Stock-based compensation expense	1,109			1,109
Stock-based compensation excess tax benefit recognized in income	(99)			(99)
Lapsed restricted stock units				(358)			358
Transfer from retained earnings/transfer to legal surplus					5,161	(5,161)
Net income	52,646					52,646
Cash dividends declared on common stock	(10,553)					(10,553)
Cash dividends declared on preferred stock	(13,862)					(13,862)
Stock purchased	0						0
Other comprehensive (loss) income, net of tax	(4,545)							(4,545)
Ending Balance at Dec. 31, 2017	$ 945,107	$ 176,000	$ 52,626	$ 541,600	$ 81,454	$ 200,878	$ (104,502)	$ (2,949)