Consolidated Statements of Shareholders’ Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Capital Surplus	Retained Earnings	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 (in shares) at Dec. 31, 2020						2,212,224
Balance at beginning of period at Dec. 31, 2020	$ 2,647,088	$ 71,754	$ 1,913,285	$ 671,510	$ 33,505	$ (42,966)
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)
Proceeds from exercise of stock options (in shares)		165,608
Proceeds from exercise of stock options	4,499	$ 166	4,333
Share-based compensation	4,896		4,896
Purchase of treasury shares (in shares)						168,267
Purchase of treasury shares	(8,108)					$ (8,108)
Net income	294,969			294,969
Dividends on common shares	(31,500)			(31,500)
Other comprehensive loss during the period	(11,620)				(11,620)
Balance at end of period (in shares) at Sep. 30, 2021		72,015,926
Balance at end of period (in shares) at Sep. 30, 2021						2,380,491
Balance at end of period at Sep. 30, 2021	2,900,770	$ 72,016	1,922,964	934,979	21,885	$ (51,074)
Balance at beginning of period (in shares) at Jun. 30, 2021		72,007,871
Balance at beginning of period (in shares) at Jun. 30, 2021						2,240,662
Balance at beginning of period at Jun. 30, 2021	2,837,004	$ 72,008	1,920,566	863,828	25,024	$ (44,422)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Forfeitures of restricted shares (in shares)		(1,945)
Forfeitures of restricted shares	(33)	$ (2)	(31)
Proceeds from exercise of stock options (in shares)		10,000
Proceeds from exercise of stock options	288	$ 10	278
Share-based compensation	2,151		2,151
Purchase of treasury shares (in shares)						139,829
Purchase of treasury shares	(6,652)					$ (6,652)
Net income	81,680			81,680
Dividends on common shares	(10,529)			(10,529)
Other comprehensive loss during the period	(3,139)				(3,139)
Balance at end of period (in shares) at Sep. 30, 2021		72,015,926
Balance at end of period (in shares) at Sep. 30, 2021						2,380,491
Balance at end of period at Sep. 30, 2021	$ 2,900,770	$ 72,016	1,922,964	934,979	21,885	$ (51,074)
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					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					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 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					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)