Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Capital Surplus	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss), Net of Tax	Treasury Stock
Balance at beginning of period (in shares) at Dec. 31, 2020			71,753,705
Balance at beginning of period at Dec. 31, 2020	$ 2,647,088		$ 71,754	$ 1,913,285	$ 671,510		$ 33,505	$ (42,966)
Balance at beginning of period (in shares) at Dec. 31, 2020								2,212,224
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted shares (in shares)			99,308
Issuance of restricted shares	599		$ 99	500
Forfeitures of restricted shares (in shares)			(2,695)
Forfeitures of restricted shares	(53)		$ (3)	(50)
Exercise of stock options (in shares)			166,808
Exercise of stock options	4,532		$ 167	4,365
Share-based compensation	6,713			6,713
Purchase of treasury shares (in shares)								195,674
Purchase of treasury shares	(9,439)							$ (9,439)
Net income	376,913				376,913
Dividends on common shares	(41,987)				(41,987)
Other comprehensive income (loss) during the period	(17,915)						(17,915)
Balance at end of period (in shares) at Dec. 31, 2021			72,017,126
Balance at end 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, 2021								2,407,898
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted shares (in shares)			165,687
Issuance of restricted shares	1,341		$ 166	1,175
Forfeitures of restricted shares (in shares)			(14,889)
Forfeitures of restricted shares	(143)		$ (15)	(128)
Exercise of stock options (in shares)			95,803
Exercise of stock options	2,799		$ 96	2,703
Share-based compensation	6,648			6,648
Purchase of treasury shares (in shares)								486,779
Purchase of treasury shares	(22,421)							$ (22,421)
Net income	346,540				346,540
Dividends on common shares	(41,718)				(41,718)
Other comprehensive income (loss) during the period	$ (62,097)						(62,097)
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-02 [Member]
Balance at end of period (in shares) at Dec. 31, 2022	72,263,727		72,263,727
Balance at end of period at Dec. 31, 2022	$ 3,197,400		$ 72,264	1,935,211	1,311,258		(46,507)	$ (74,826)
Balance at end of period (in shares) at Dec. 31, 2022	2,894,677							2,894,677
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle for ASU 2022-02		$ 1,277				$ 1,277
Issuance of restricted shares (in shares)			133,430
Issuance of restricted shares	$ 0		$ 133	(133)
Issuance of common shares pursuant to PSU agreements (in shares)			105,005
Issuance of common shares pursuant to PSU agreements	0		$ 105	(105)
Forfeitures of restricted shares (in shares)			(2,083)
Forfeitures of restricted shares	(32)		$ (2)	(30)
Exercise of stock options (in shares)			16,000
Exercise of stock options	476		$ 16	460
Share-based compensation	9,982			9,982
Purchase of treasury shares (in shares)								568,061
Purchase of treasury shares	(20,346)							$ (20,346)
Net income	269,105				269,105
Dividends on common shares	(41,683)				(41,683)
Other comprehensive income (loss) during the period	$ 10,568						10,568
Balance at end of period (in shares) at Dec. 31, 2023	72,516,079		72,516,079
Balance at end of period at Dec. 31, 2023	$ 3,426,747		$ 72,516	$ 1,945,385	$ 1,539,957		$ (35,939)	$ (95,172)
Balance at end of period (in shares) at Dec. 31, 2023	3,462,738							3,462,738