Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative adjustment upon adoption of ASU 2016-13 [ Member]	Common Stock [Member]	Common Stock [Member] Cumulative adjustment upon adoption of ASU 2016-13 [ Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative adjustment upon adoption of ASU 2016-13 [ Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Cumulative adjustment upon adoption of ASU 2016-13 [ Member]
Beginning balance at Dec. 31, 2019	$ 1,994,098	$ (1,325)	$ 1,298,792	$ 0	$ 682,692	$ (1,325)	$ 12,614	$ 0
Beginning balance, shares at Dec. 31, 2019			140,102	0
Repurchase of common stock	(92,402)		$ (92,402)
Repurchase of common stock, shares			(4,988)
Exercise of stock options	42		$ 42
Exercise of stock options, shares			4
Shares issued pursuant to stock-based compensation plan	1,617		$ 1,617
Shares issued pursuant to stock-based compensation plan, shares			393
Cash dividends declared on common stock	(24,416)				(24,416)
Net earnings	37,980				37,980
Other comprehensive income (loss)	25,792						25,792
Ending balance at Mar. 31, 2020	1,941,386		$ 1,208,049		694,931		38,406
Ending balance, shares at Mar. 31, 2020			135,511
Beginning balance at Dec. 31, 2020	2,007,990		$ 1,211,780		760,861		35,349
Beginning balance, shares at Dec. 31, 2020			135,601
Repurchase of common stock	(502)		$ (502)
Repurchase of common stock, shares			(22)
Exercise of stock options	891		$ 891
Exercise of stock options, shares			40
Shares issued pursuant to stock-based compensation plan	1,282		$ 1,282
Shares issued pursuant to stock-based compensation plan, shares			301
Cash dividends declared on common stock	(24,495)				(24,495)
Net earnings	63,893				63,893
Other comprehensive income (loss)	(28,393)						(28,393)
Ending balance at Mar. 31, 2021	$ 2,020,666		$ 1,213,451		$ 800,259		$ 6,956
Ending balance, shares at Mar. 31, 2021			135,920