CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	3 Months Ended							9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2021
Statement of Stockholders' Equity [Abstract]
Common Stock, Dividends, Per Share, Declared	$ 0.48	$ 0.48	$ 0.48	$ 0.44	$ 0.44	$ 0.44	$ 0.44	$ 1.44	$ 1.32
Net Income (Loss) Attributable to Parent	$ 45,854	$ 39,591	$ 55,555	$ 54,380	$ 49,070	$ 47,965	$ 43,963	$ 141,000	$ 140,998
Other Comprehensive Income (Loss), Net of Tax	(53,467)		37,133	6,421	(113,275)	(101,824)	(154,275)	(30,146)	(369,374)
Accrual of dividends on common stock	(16,666)	(16,670)	(16,691)	(15,246)	(15,208)	(15,378)	(15,066)
Amortization of stock-based compensation related to restricted stock grants, net of shares surrendered	2,373	1,709	(734)	2,218	2,242	2,247	(1,169)
Repurchase of common stock						(10,960)
Equity, Attributable to Parent	$ 1,520,607	$ 1,542,513	$ 1,531,695	$ 1,456,432	$ 1,408,659	$ 1,485,830	$ 1,563,780	$ 1,520,607	$ 1,408,659	$ 1,690,327
Common Stock, Dividends, Per Share, Declared	$ 0.48	$ 0.48	$ 0.48	$ 0.44	$ 0.44	$ 0.44	$ 0.44	$ 1.44	$ 1.32
Common Stock [Member]
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture	1,322	36,087	114,522	2,259	429	18,546	120,152
Stock Repurchased and Retired During Period, Shares						(200,000)
Shares, Outstanding	34,345,949	34,344,627	34,308,540	34,194,018	34,191,759	34,191,330	34,372,784	34,345,949	34,191,759	34,252,632
Common Stock and Paid in Capital [Member]
Amortization of stock-based compensation related to restricted stock grants, net of shares surrendered	$ 2,373	$ 1,709	$ (734)	$ 2,218	$ 2,242	$ 2,247	$ (1,169)
Repurchase of common stock						(10,960)
Equity, Attributable to Parent	1,297,307	1,294,934	1,293,225	1,293,959	1,291,741	1,289,499	1,298,212	$ 1,297,307	$ 1,291,741	$ 1,299,381
Retained Earnings [Member]
Net Income (Loss) Attributable to Parent	45,854	39,591	55,555	54,380	49,070	47,965	43,963
Accrual of dividends on common stock	(16,666)	(16,670)	(16,691)	(15,246)	(15,208)	(15,378)	(15,066)
Equity, Attributable to Parent	616,215	587,027	564,106	525,242	486,108	452,246	419,659	616,215	486,108	390,762
Accumulated Other Comprehensive Income (Loss) [Member]
Other Comprehensive Income (Loss), Net of Tax			37,133	6,421	(113,275)	(101,824)	(154,275)
Equity, Attributable to Parent	$ (392,915)	$ (339,448)	$ (325,636)	$ (362,769)	$ (369,190)	$ (255,915)	$ (154,091)	$ (392,915)	$ (369,190)	$ 184