Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect Adjustments [Member]	Adjusted Balance [Member]	Common Stock	Common Stock Adjusted Balance [Member]	Capital Surplus	Capital Surplus Adjusted Balance [Member]	Retained Earnings	Retained Earnings Cumulative Effect Adjustments [Member]	Retained Earnings Adjusted Balance [Member]	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Adjusted Balance [Member]	Treasury Stock	Treasury Stock Adjusted Balance [Member]
Beginning Balance at Dec. 31, 2019	$ 2,606,440	$ (7,039)	$ 2,599,401	$ 55,057	$ 55,057	$ 1,073,764	$ 1,073,764	$ 1,672,438	$ (7,039)	$ 1,665,399	$ 83,180	$ 83,180	$ (277,999)	$ (277,999)
Total comprehensive income (loss)	132,771							(3,439)			136,210
Dividends	(15,209)							(15,209)
Purchase of treasury stock	(59,386)					(4,500)							(54,886)
Forfeitures of equity awards, net of issuances	593					521							72
Recognition of equity-based compensation	2,817					2,817
Sale of treasury stock	184					95							89
Exercise of stock options	2,270					392							1,878
Ending Balance at Mar. 31, 2020	2,663,441			55,057		1,073,089		1,646,751			219,390		(330,846)
Beginning Balance at Dec. 31, 2020	3,016,948			55,057		1,090,450		1,891,246			318,340		(338,145)
Total comprehensive income (loss)	(56,500)							92,643			(149,143)
Dividends	(15,571)							(15,571)
Purchase of treasury stock	(4,027)												(4,027)
Forfeitures of equity awards, net of issuances	695					(4,043)							4,738
Recognition of equity-based compensation	4,457					4,457
Sale of treasury stock	151					65							86
Exercise of stock options	12,086					2,738							9,348
Ending Balance at Mar. 31, 2021	$ 2,958,239			$ 55,057		$ 1,093,667		$ 1,968,318			$ 169,197		$ (328,000)