Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands		Total	Preferred Stock	Voting Common Stock, par value $1.00 per share	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2016		$ 855,872	$ 217,471	$ 30,820	$ 427,008	$ 193,698	$ (4,892)	$ (8,233)
Beginning balance, preferred stock (shares) at Dec. 31, 2016			9,000,000
Beginning balance, common stock (shares) at Dec. 31, 2016				30,289,917
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		78,837				78,837
Other comprehensive income (loss)		4,533					4,533
Preferred stock dividends	[1]	(14,459)				(14,459)
Share-based compensation expense		6,088			6,088
Exercise of warrants (shares)				74,161
Exercise of warrants		1,059		$ 74	985
Issuance of common stock under share-based-compensation arrangements (shares)				1,018,425
Issuance of common stock under share-based-compensation arrangements		$ (10,966)		$ 1,019	(11,985)
Repurchase of common shares (shares)		0
Ending balance at Dec. 31, 2017		$ 920,964	$ 217,471	$ 31,913	422,096	258,076	(359)	(8,233)
Ending balance, preferred stock (shares) at Dec. 31, 2017			9,000,000
Ending balance, common stock (shares) at Dec. 31, 2017				31,382,503
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		71,695				71,695
Other comprehensive income (loss)		(20,965)					(20,965)
Preferred stock dividends	[1]	(14,459)				(14,459)
Share-based compensation expense		8,605			8,605
Exercise of warrants (shares)				5,242
Exercise of warrants		112		$ 5	107
Issuance of common stock under share-based-compensation arrangements (shares)				334,483
Issuance of common stock under share-based-compensation arrangements		$ 3,840		$ 334	3,506
Repurchase of common shares (shares)		(719,200)		(719,200)
Repurchase of common shares, value		$ (12,976)						(12,976)
Ending balance at Dec. 31, 2018		$ 956,816	$ 217,471	$ 32,252	434,314	316,651	(22,663)	(21,209)
Ending balance, preferred stock (shares) at Dec. 31, 2018		9,000,000	9,000,000
Ending balance, common stock (shares) at Dec. 31, 2018		31,003,028		31,003,028
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 79,327				79,327
Other comprehensive income (loss)		21,413					21,413
Preferred stock dividends	[1]	(14,459)				(14,459)
Share-based compensation expense		8,898			8,898
Issuance of common stock under share-based-compensation arrangements (shares)				364,922
Issuance of common stock under share-based-compensation arrangements		1,371		$ 365	1,006
Repurchase of common shares (shares)				(31,159)
Repurchase of common shares, value		(571)						(571)
Ending balance at Dec. 31, 2019		$ 1,052,795	$ 217,471	$ 32,617	$ 444,218	$ 381,519	$ (1,250)	$ (21,780)
Ending balance, preferred stock (shares) at Dec. 31, 2019		9,000,000	9,000,000
Ending balance, common stock (shares) at Dec. 31, 2019		31,336,791		31,336,791

[1] Dividends per share of $1.75, $1.63, $1.61, and $1.50 per share were declared on Series C, D, E, and F preferred stock for the years ended December 31, 2019, 2018, and 2017, respectively.