Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock Outstanding [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Treasury Stock, Common [Member]	Total
Balance (in shares) at Dec. 31, 2021	75,750,862
Beginning balance, loss, net of tax at Dec. 31, 2021	$ 909	$ 972,474	$ (3,065)	$ 1,985,168	$ (509,235)	$ 2,446,251
Dividend Reinvestment Plan (in shares)	65,142
Dividend Reinvestment Plan	$ 1	2,791	0	0	0	2,792
Restricted stock units vested (in shares)	110,641
Restricted stock units vested	$ 1	0	0	0	0	1
Shares withheld related to net share settlement of RSUs	0	(2,864)	0	0	0	(2,864)
Purchases of treasury stock	0	0	0	0	(109,774)	(109,774)
Stock-based compensation	0	5,183	0	0	0	5,183
Cash dividends	0	0	0	(76,111)	0	(76,111)
Other comprehensive income/(loss)	0	0	(109,809)	0	0	(109,809)
Net income	$ 0	0	0	263,041	0	263,041
Purchases of treasury stock (in shares)	(2,534,465)
Stock issued to directors (in shares)	19,780
Stock issued to directors	$ 0	849	0	0	0	849
Other comprehensive loss	$ 0	0	(109,809)	0	0	(109,809)
Balance (in shares) at Sep. 30, 2022	73,411,960
Ending balance, loss, net of tax at Sep. 30, 2022	$ 911	978,433	(112,874)	2,172,098	(619,009)	2,419,559
Balance (in shares) at Dec. 31, 2021	75,750,862
Beginning balance, loss, net of tax at Dec. 31, 2021	$ 909	972,474	(3,065)	1,985,168	(509,235)	2,446,251
Shares withheld related to net share settlement of RSUs						(3,500)
Purchases of treasury stock						(16,700)
Balance (in shares) at Sep. 30, 2023	72,586,992
Ending balance, loss, net of tax at Sep. 30, 2023	$ 913	986,074	(123,533)	2,442,516	(667,234)	2,638,736
Balance (in shares) at Jun. 30, 2022	74,421,884
Beginning balance, loss, net of tax at Jun. 30, 2022	$ 910	976,547	(71,328)	2,098,122	(572,719)	2,431,532
Dividend Reinvestment Plan (in shares)	21,880
Dividend Reinvestment Plan	$ 1	919	0	0	0	920
Restricted stock units vested (in shares)	47,736
Restricted stock units vested	$ 0	0	0	0	0	0
Shares withheld related to net share settlement of RSUs	0	(849)	0	0	0	(849)
Purchases of treasury stock	0	0	0	0	(46,290)	(46,290)
Stock-based compensation	0	1,816	0	0	0	1,816
Cash dividends	0	0	0	(25,059)	0	(25,059)
Other comprehensive income/(loss)	0	0	(41,546)	0	0	(41,546)
Net income	$ 0	0	0	99,035	0	99,035
Purchases of treasury stock (in shares)	(1,079,540)
Other comprehensive loss	$ 0	0	(41,546)	0	0	(41,546)
Balance (in shares) at Sep. 30, 2022	73,411,960
Ending balance, loss, net of tax at Sep. 30, 2022	$ 911	978,433	(112,874)	2,172,098	(619,009)	2,419,559
Balance (in shares) at Dec. 31, 2022	72,742,151
Beginning balance, loss, net of tax at Dec. 31, 2022	$ 911	981,119	(102,295)	2,244,856	(650,551)	2,474,040
Dividend Reinvestment Plan (in shares)	73,269
Dividend Reinvestment Plan	$ 1	2,698	0	0	0	2,699
Restricted stock units vested (in shares)	121,302
Restricted stock units vested	$ 1	0	0	0	0	1
Shares withheld related to net share settlement of RSUs	0	(3,538)	0	0	0	(3,538)
Purchases of treasury stock	0	0	0	0	(16,683)	(16,683)
Stock-based compensation	0	4,945	0	0	0	4,945
Cash dividends	0	0	0	(73,938)	0	(73,938)
Other comprehensive income/(loss)	0	0	(21,238)	0	0	(21,238)
Net income	$ 0	0	0	271,598	0	271,598
Purchases of treasury stock (in shares)	(375,090)
Stock issued to directors (in shares)	25,360
Stock issued to directors	$ 0	850	0	0	0	850
Other comprehensive loss	$ 0	0	(21,238)	0	0	(21,238)
Balance (in shares) at Sep. 30, 2023	72,586,992
Ending balance, loss, net of tax at Sep. 30, 2023	$ 913	986,074	(123,533)	2,442,516	(667,234)	2,638,736
Balance (in shares) at Jun. 30, 2023	72,563,169
Beginning balance, loss, net of tax at Jun. 30, 2023	$ 913	983,233	(99,049)	2,384,817	(667,243)	2,602,671
Dividend Reinvestment Plan (in shares)	23,397
Dividend Reinvestment Plan	$ 0	865	0	0	0	865
Restricted stock units vested (in shares)	426
Restricted stock units vested	$ 0	0	0	0	0	0
Shares withheld related to net share settlement of RSUs	0	(11)	0	0	0	(11)
Purchases of treasury stock	0	0	0	0	(9)	(9)
Stock-based compensation	0	1,987	0	0	0	1,987
Cash dividends	0	0	0	(24,672)	0	(24,672)
Other comprehensive income/(loss)	0	0	(24,484)	0	0	(24,484)
Net income	0	0	0	82,371	0	82,371
Other comprehensive loss	$ 0	0	(24,484)	0	0	(24,484)
Balance (in shares) at Sep. 30, 2023	72,586,992
Ending balance, loss, net of tax at Sep. 30, 2023	$ 913	$ 986,074	$ (123,533)	$ 2,442,516	$ (667,234)	$ 2,638,736