Consolidated Statements of Shareholders’ Equity (unaudited) - USD ($) $ in Thousands	Total	Cumulative effect of change in accounting principle for ASU 2022-02	Common Stock	Capital Surplus	Retained Earnings	Retained Earnings Cumulative effect of change in accounting principle for ASU 2022-02	Accumulated Other Comprehensive Income (Loss), Net of Tax	Treasury Stock
Balance at beginning of period (in shares) at Dec. 31, 2021			72,017,126
Balance at beginning of period (in shares) at Dec. 31, 2021								2,407,898
Balance at beginning of period at Dec. 31, 2021	$ 2,966,451		$ 72,017	$ 1,924,813	$ 1,006,436		$ 15,590	$ (52,405)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted shares (in shares)			164,346
Issuance of restricted shares	1,341		$ 164	1,177
Forfeitures of restricted shares (in shares)			(13,889)
Forfeitures of restricted shares	(133)		$ (14)	(119)
Proceeds from exercise of stock options (in shares)			79,803
Proceeds from exercise of stock options	2,324		$ 80	2,244
Share-based compensation	4,791			4,791
Purchase of treasury shares (in shares)								486,779
Purchase of treasury shares	(22,421)							$ (22,421)
Net income	264,319				264,319
Dividends on common shares	(31,278)				(31,278)
Other comprehensive loss during the period	(66,324)						(66,324)
Balance at end of period (in shares) at Sep. 30, 2022			72,247,386
Balance at end of period (in shares) at Sep. 30, 2022								2,894,677
Balance at end of period at Sep. 30, 2022	3,119,070		$ 72,247	1,932,906	1,239,477		(50,734)	$ (74,826)
Balance at beginning of period (in shares) at Dec. 31, 2021			72,017,126
Balance at beginning of period (in shares) at Dec. 31, 2021								2,407,898
Balance at beginning of period at Dec. 31, 2021	$ 2,966,451		$ 72,017	1,924,813	1,006,436		15,590	$ (52,405)
Balance at end of period (in shares) at Dec. 31, 2022	72,263,727		72,263,727
Balance at end of period (in shares) at Dec. 31, 2022	2,894,677							2,894,677
Balance at end of period at Dec. 31, 2022	$ 3,197,400	$ 1,277	$ 72,264	1,935,211	1,311,258	$ 1,277	(46,507)	$ (74,826)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-02 [Member]
Balance at beginning of period (in shares) at Jun. 30, 2022			72,251,856
Balance at beginning of period (in shares) at Jun. 30, 2022								2,891,395
Balance at beginning of period at Jun. 30, 2022	$ 3,073,376		$ 72,251	1,931,088	1,157,359		(12,635)	$ (74,687)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Forfeitures of restricted shares (in shares)			(4,470)
Forfeitures of restricted shares	(42)		$ (4)	(38)
Share-based compensation	1,856			1,856
Purchase of treasury shares (in shares)								3,282
Purchase of treasury shares	(139)							$ (139)
Net income	92,555				92,555
Dividends on common shares	(10,437)				(10,437)
Other comprehensive loss during the period	(38,099)						(38,099)
Balance at end of period (in shares) at Sep. 30, 2022			72,247,386
Balance at end of period (in shares) at Sep. 30, 2022								2,894,677
Balance at end of period at Sep. 30, 2022	$ 3,119,070		$ 72,247	1,932,906	1,239,477		(50,734)	$ (74,826)
Balance at beginning of period (in shares) at Dec. 31, 2022	72,263,727		72,263,727
Balance at beginning of period (in shares) at Dec. 31, 2022	2,894,677							2,894,677
Balance at beginning of period at Dec. 31, 2022	$ 3,197,400	$ 1,277	$ 72,264	1,935,211	1,311,258	$ 1,277	(46,507)	$ (74,826)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted shares (in shares)			133,430
Issuance of restricted shares	0		$ 134	(134)
Issuance of common shares pursuant to PSU agreements (in shares)			102,973
Issuance of common shares pursuant to PSU agreements	0		$ 103	(103)
Forfeitures of restricted shares (in shares)			(2,083)
Forfeitures of restricted shares	(33)		$ (3)	(30)
Proceeds from exercise of stock options (in shares)			16,000
Proceeds from exercise of stock options	476		$ 16	460
Share-based compensation	7,448			7,448
Purchase of treasury shares (in shares)								480,909
Purchase of treasury shares	(17,077)							$ (17,077)
Net income	203,171				203,171
Dividends on common shares	(31,282)				(31,282)
Other comprehensive loss during the period	$ (14,311)						(14,311)
Balance at end of period (in shares) at Sep. 30, 2023	72,514,047		72,514,047
Balance at end of period (in shares) at Sep. 30, 2023	3,375,586							3,375,586
Balance at end of period at Sep. 30, 2023	$ 3,347,069		$ 72,514	1,942,852	1,484,424		(60,818)	$ (91,903)
Balance at beginning of period (in shares) at Jun. 30, 2023			72,514,630
Balance at beginning of period (in shares) at Jun. 30, 2023								3,374,847
Balance at beginning of period at Jun. 30, 2023	3,284,630		$ 72,515	1,939,865	1,414,742		(50,618)	$ (91,874)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted shares (in shares)			1,500
Issuance of restricted shares	0		$ 2	(2)
Forfeitures of restricted shares (in shares)			(2,083)
Forfeitures of restricted shares	(33)		$ (3)	(30)
Share-based compensation	3,019			3,019
Purchase of treasury shares (in shares)								739
Purchase of treasury shares	(29)							$ (29)
Net income	80,115				80,115
Dividends on common shares	(10,433)				(10,433)
Other comprehensive loss during the period	$ (10,200)						(10,200)
Balance at end of period (in shares) at Sep. 30, 2023	72,514,047		72,514,047
Balance at end of period (in shares) at Sep. 30, 2023	3,375,586							3,375,586
Balance at end of period at Sep. 30, 2023	$ 3,347,069		$ 72,514	$ 1,942,852	$ 1,484,424		$ (60,818)	$ (91,903)