CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Treasury Stock	Deferred Compensation Arrangements	Total
Balance at Dec. 31, 2020	$ 53,755	$ 1,025,163	$ 960,183	$ 62,077	$ (6,198)	$ 9,127	$ 2,104,107
Balance (in shares) at Dec. 31, 2020	53,593,127
Increase (Decrease) in Stockholders' Equity
Net income			146,130				146,130
Other comprehensive loss, net of tax				(125,903)			(125,903)
Dividends declared:
Common			(68,377)				(68,377)
Common stock activity under employee stock plans	$ 317	8,824					9,141
Common stock activity under employee stock plans (in shares)	317,390
Stock-based compensation		4,836					4,836
Distribution of stock under deferred compensation arrangements		323			694	(1,017)	0
Distribution of stock under deferred compensation arrangements (in shares)	18,089
Treasury stock issued to benefit plans, net					(189)	189	0
Treasury stock issued to benefit plans, net (in shares)	(2,619)
Balance at Sep. 30, 2021	$ 54,072	1,039,146	1,037,936	(63,826)	(5,693)	8,299	2,069,934
Balance (in shares) at Sep. 30, 2021	53,925,987
Balance at Jun. 30, 2021	$ 54,064	1,037,088	1,015,742	(48,400)	(5,632)	8,238	2,061,100
Balance (in shares) at Jun. 30, 2021	53,918,695
Increase (Decrease) in Stockholders' Equity
Net income			45,336				45,336
Other comprehensive loss, net of tax				(15,426)			(15,426)
Dividends declared:
Common			(23,142)				(23,142)
Common stock activity under employee stock plans	$ 8	464					472
Common stock activity under employee stock plans (in shares)	8,122
Stock-based compensation		1,594					1,594
Treasury stock issued to benefit plans, net					(61)	61	0
Treasury stock issued to benefit plans, net (in shares)	(830)
Balance at Sep. 30, 2021	$ 54,072	1,039,146	1,037,936	(63,826)	(5,693)	8,299	2,069,934
Balance (in shares) at Sep. 30, 2021	53,925,987
Balance at Dec. 31, 2021	$ 54,092	1,041,304	1,058,286	(50,627)	(10,610)	8,362	2,100,807
Balance (in shares) at Dec. 31, 2021	53,878,047
Increase (Decrease) in Stockholders' Equity
Net income			135,551				135,551
Other comprehensive loss, net of tax				(695,754)			(695,754)
Dividends declared:
Common			(70,196)				(70,196)
Common stock activity under employee stock plans	$ 96	990					1,086
Common stock activity under employee stock plans (in shares)	95,586
Stock-based compensation		6,047					6,047
Distribution of stock under deferred compensation arrangements		103			739	(842)	0
Distribution of stock under deferred compensation arrangements (in shares)	14,934
Treasury stock purchased					(16,378)		(16,378)
Treasury stock purchased (in shares)	(250,000)
Treasury stock issued to benefit plans, net					(177)	177	0
Treasury stock issued to benefit plans, net (in shares)	(2,551)
Balance at Sep. 30, 2022	$ 54,188	1,048,444	1,123,641	(746,381)	(26,426)	7,697	1,461,163
Balance (in shares) at Sep. 30, 2022	53,736,016
Balance at Jun. 30, 2022	$ 54,185	1,046,303	1,098,664	(518,727)	(26,369)	7,640	1,661,696
Balance (in shares) at Jun. 30, 2022	53,734,027
Increase (Decrease) in Stockholders' Equity
Net income			48,691				48,691
Other comprehensive loss, net of tax				(227,654)			(227,654)
Dividends declared:
Common			(23,714)				(23,714)
Common stock activity under employee stock plans	$ 3	284					287
Common stock activity under employee stock plans (in shares)	2,892
Stock-based compensation		1,857					1,857
Treasury stock issued to benefit plans, net					(57)	57	0
Treasury stock issued to benefit plans, net (in shares)	(903)
Balance at Sep. 30, 2022	$ 54,188	$ 1,048,444	$ 1,123,641	$ (746,381)	$ (26,426)	$ 7,697	$ 1,461,163
Balance (in shares) at Sep. 30, 2022	53,736,016