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	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)	49,469				49,469
Other comprehensive income	10,256					10,256
Preferred stock dividends	(7,229)				(7,229)
Share-based compensation expense	2,934			2,934
Exercise of warrants (shares)			43,974
Exercise of warrants	420		$ 44	376
Issuance of common stock under share-based compensation arrangements (shares)			396,893
Issuance of common stock under share-based compensation arrangements	(1,433)		$ 397	(1,830)
Ending balance, preferred stock (shares) at Jun. 30, 2017		9,000,000
Ending balance, common stock (shares) at Jun. 30, 2017			30,730,784
Ending balance at Jun. 30, 2017	910,289	$ 217,471	$ 31,261	428,488	235,938	5,364	(8,233)
Beginning balance at Mar. 31, 2017						(4,872)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	23,722
Other comprehensive income	10,236
Ending balance, preferred stock (shares) at Jun. 30, 2017		9,000,000
Ending balance, common stock (shares) at Jun. 30, 2017			30,730,784
Ending 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]
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2018-02	0
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2016-01	$ 0
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)	47,804				47,804
Other comprehensive income	(32,299)					(32,299)
Preferred stock dividends	(7,229)				(7,229)
Share-based compensation expense	3,661			3,661
Exercise of warrants (shares)			5,242
Exercise of warrants	112		$ 5	107
Issuance of common stock under share-based compensation arrangements (shares)			281,898
Issuance of common stock under share-based compensation arrangements	$ 3,214		$ 282	2,932
Ending balance, preferred stock (shares) at Jun. 30, 2018	9,000,000	9,000,000
Ending balance, common stock (shares) at Jun. 30, 2018	31,669,643		31,669,643
Ending balance at Jun. 30, 2018	$ 936,227	$ 217,471	$ 32,200	428,796	299,990	(33,997)	(8,233)
Beginning balance at Mar. 31, 2018						(26,188)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	23,663
Other comprehensive income	$ (7,809)
Ending balance, preferred stock (shares) at Jun. 30, 2018	9,000,000	9,000,000
Ending balance, common stock (shares) at Jun. 30, 2018	31,669,643		31,669,643
Ending balance at Jun. 30, 2018	$ 936,227	$ 217,471	$ 32,200	$ 428,796	$ 299,990	$ (33,997)	$ (8,233)