Consolidated Statements of Changes in Shareholders' Equity - Unaudited - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Treasury Stock
Beginning balance, preferred stock (shares) at Dec. 31, 2016		9,000,000
Beginning balance, common stock (shares) at Dec. 31, 2016			30,289,917
Beginning balance at Dec. 31, 2016	$ 855,872	$ 217,471	$ 30,820	$ 427,008	$ 193,698	$ (4,892)	$ (8,233)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	57,222				57,222
Other comprehensive income (loss)	5,269					5,269
Preferred stock dividends	(10,844)				(10,844)
Share-based compensation expense	4,536			4,536
Exercise of warrants (shares)			50,387
Exercise of warrants	557		$ 50	507
Issuance of common stock under share-based compensation arrangements (shares)			447,328
Issuance of common stock under share-based compensation arrangements	(1,970)		$ 448	(2,418)
Ending balance, preferred stock (shares) at Sep. 30, 2017		9,000,000
Ending balance, common stock (shares) at Sep. 30, 2017			30,787,632
Ending balance at Sep. 30, 2017	910,642	$ 217,471	$ 31,318	429,633	240,076	377	(8,233)
Beginning balance, preferred stock (shares) at Jun. 30, 2017		9,000,000
Beginning balance, common stock (shares) at Jun. 30, 2017			30,730,784
Beginning balance at Jun. 30, 2017	910,289	$ 217,471	$ 31,261	428,488	235,938	5,364	(8,233)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	7,754				7,754
Other comprehensive income (loss)	(4,987)					(4,987)
Preferred stock dividends	(3,615)				(3,615)
Share-based compensation expense	1,602			1,602
Exercise of warrants (shares)			6,413
Exercise of warrants	137		$ 6	131
Issuance of common stock under share-based compensation arrangements (shares)			50,435
Issuance of common stock under share-based compensation arrangements	(538)		$ 51	(588)	(1)
Ending balance, preferred stock (shares) at Sep. 30, 2017		9,000,000
Ending balance, common stock (shares) at Sep. 30, 2017			30,787,632
Ending balance at Sep. 30, 2017	$ 910,642	$ 217,471	$ 31,318	429,633	240,076	377	(8,233)
Beginning balance, preferred stock (shares) at Dec. 31, 2017	9,000,000	9,000,000
Beginning balance, common stock (shares) at Dec. 31, 2017	30,820,177		31,382,503
Beginning balance at Dec. 31, 2017	$ 920,964	$ 217,471	$ 31,913	422,096	258,076	(359)	(8,233)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	53,833				53,833
Other comprehensive income (loss)	(18,555)					(18,555)
Preferred stock dividends	(10,844)				(10,844)
Share-based compensation expense	5,641			5,641
Exercise of warrants (shares)			5,242
Exercise of warrants	112		$ 5	107
Issuance of common stock under share-based compensation arrangements (shares)			299,595
Issuance of common stock under share-based compensation arrangements	$ 3,661		$ 300	3,361
Ending balance, preferred stock (shares) at Sep. 30, 2018	9,000,000	9,000,000
Ending balance, common stock (shares) at Sep. 30, 2018	31,687,340		31,687,340
Ending balance at Sep. 30, 2018	$ 954,812	$ 217,471	$ 32,218	431,205	302,404	(20,253)	(8,233)
Beginning balance, preferred stock (shares) at Jun. 30, 2018		9,000,000
Beginning balance, common stock (shares) at Jun. 30, 2018			31,669,643
Beginning balance at Jun. 30, 2018	936,227	$ 217,471	$ 32,200	428,796	299,990	(33,997)	(8,233)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	6,029				6,029
Other comprehensive income (loss)	13,744					13,744
Preferred stock dividends	(3,615)				(3,615)
Share-based compensation expense	1,980			1,980
Issuance of common stock under share-based compensation arrangements (shares)			17,697
Issuance of common stock under share-based compensation arrangements	$ 447		$ 18	429
Ending balance, preferred stock (shares) at Sep. 30, 2018	9,000,000	9,000,000
Ending balance, common stock (shares) at Sep. 30, 2018	31,687,340		31,687,340
Ending balance at Sep. 30, 2018	$ 954,812	$ 217,471	$ 32,218	$ 431,205	$ 302,404	$ (20,253)	$ (8,233)