Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional paid-in capital [Member]	Retained Earnings [Member]	Accumulated other comprehensive income (loss) [Member]	Treasury stock [Member]
Preferred Stock, Shares Outstanding	8,000
Beginning of period at Dec. 31, 2020		$ 200,000	$ 208,066	$ 438,985	$ 2,271,537	$ 220,186	$ (599,885)
Issuance of preferred stock		0
Dividend reinvestment plan			34	1,261
Stock purchase and compensation plans			678	17,897
Net income	$ 304,858				304,858
Dividends to preferred stockholders					(7,053)
Dividends to common stockholders					(45,532)
Other comprehensive loss	(79,962)					(79,962)
Acquisition of treasury stock - share repurchase authorization							(3,404)
Acquisition of treasury stock - shares acquired related to employee-share based compensation plans							(5,570)
End of period at Sep. 30, 2021	$ 2,922,096	$ 200,000	208,778	458,143	2,523,810	140,224	(608,859)
Dividends declared per share to preferred stockholders	$ 881.67
Dividends declared per share to common stockholders	$ 0.75
Issuance of preferred stock, shares		0
Common stock, shares outstanding, beginning of period at Dec. 31, 2020	59,905,803
Dividend reinvestment plan, shares	17,152
Stock purchase and compensation plan, shares	339,061
Acquisition of treasury stock, share repurchase authorization, shares	(52,781)
Acquisition of treasury stock - shares acquired related to employee share-based compensation plans, shares	(85,700)
Common stock, shares outstanding, end of period at Sep. 30, 2021	60,123,535
Preferred Stock, Shares Outstanding	8,000
Beginning of period at Jun. 30, 2021		$ 200,000	208,742	454,459	2,467,596	169,371	(608,801)
Issuance of preferred stock		0
Dividend reinvestment plan			10	416
Stock purchase and compensation plans			26	3,268
Net income	$ 73,705				73,705
Dividends to preferred stockholders					(2,300)
Dividends to common stockholders					(15,191)
Other comprehensive loss	(29,147)					(29,147)
Acquisition of treasury stock - share repurchase authorization							0
Acquisition of treasury stock - shares acquired related to employee-share based compensation plans							(58)
End of period at Sep. 30, 2021	$ 2,922,096	$ 200,000	208,778	458,143	2,523,810	140,224	(608,859)
Dividends declared per share to preferred stockholders	$ 287.50
Dividends declared per share to common stockholders	$ 0.25
Issuance of preferred stock, shares		0
Common stock, shares outstanding, beginning of period at Jun. 30, 2021	60,106,236
Dividend reinvestment plan, shares	5,096
Stock purchase and compensation plan, shares	12,946
Acquisition of treasury stock, share repurchase authorization, shares	0
Acquisition of treasury stock - shares acquired related to employee share-based compensation plans, shares	(743)
Common stock, shares outstanding, end of period at Sep. 30, 2021	60,123,535
Preferred Stock, Shares Outstanding	8,000
Preferred Stock, Shares Outstanding	8,000
Beginning of period at Dec. 31, 2021	$ 2,982,885	$ 200,000	208,902	464,347	2,603,472	115,099	(608,935)
Issuance of preferred stock		0
Dividend reinvestment plan			34	1,325
Stock purchase and compensation plans			622	20,567
Net income	138,375				138,375
Dividends to preferred stockholders					(6,900)
Dividends to common stockholders					(51,184)
Other comprehensive loss	(640,110)					(640,110)
Acquisition of treasury stock - share repurchase authorization	(12,400)						(12,423)
Acquisition of treasury stock - shares acquired related to employee-share based compensation plans							(5,658)
End of period at Sep. 30, 2022	$ 2,427,533	$ 200,000	209,558	486,239	2,683,763	(525,011)	(627,016)
Dividends declared per share to preferred stockholders	$ 862.50
Dividends declared per share to common stockholders	$ 0.84
Issuance of preferred stock, shares		0
Common stock, shares outstanding, beginning of period at Dec. 31, 2021	60,184,382
Dividend reinvestment plan, shares	17,152
Stock purchase and compensation plan, shares	310,760
Acquisition of treasury stock, share repurchase authorization, shares	(165,159)
Acquisition of treasury stock - shares acquired related to employee share-based compensation plans, shares	(73,644)
Common stock, shares outstanding, end of period at Sep. 30, 2022	60,273,491
Preferred Stock, Shares Outstanding	8,000
Beginning of period at Jun. 30, 2022		$ 200,000	209,506	481,380	2,660,584	(336,370)	(621,010)
Issuance of preferred stock		0
Dividend reinvestment plan			11	438
Stock purchase and compensation plans			41	4,421
Net income	$ 42,525				42,525
Dividends to preferred stockholders					(2,300)
Dividends to common stockholders					(17,046)
Other comprehensive loss	(188,641)					(188,641)
Acquisition of treasury stock - share repurchase authorization							(5,931)
Acquisition of treasury stock - shares acquired related to employee-share based compensation plans							(75)
End of period at Sep. 30, 2022	$ 2,427,533	$ 200,000	$ 209,558	$ 486,239	$ 2,683,763	$ (525,011)	$ (627,016)
Dividends declared per share to preferred stockholders	$ 287.50
Dividends declared per share to common stockholders	$ 0.28
Issuance of preferred stock, shares		0
Common stock, shares outstanding, beginning of period at Jun. 30, 2022	60,327,734
Dividend reinvestment plan, shares	5,647
Stock purchase and compensation plan, shares	20,073
Acquisition of treasury stock, share repurchase authorization, shares	(79,100)
Acquisition of treasury stock - shares acquired related to employee share-based compensation plans, shares	(863)
Common stock, shares outstanding, end of period at Sep. 30, 2022	60,273,491
Preferred Stock, Shares Outstanding	8,000