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)	258,172							57,090			201,082
Dividends	(30,200)							(30,200)
Purchase of treasury stock	(59,459)					615							(60,074)
Forfeitures of equity awards, net of issuances	593					676							(83)
Recognition of equity-based compensation	6,109					6,109
Sale of treasury stock	321					120							201
Exercise of stock options	2,458					429							2,029
Ending Balance at Jun. 30, 2020	2,777,395			55,057		1,081,713		1,692,289			284,262		(335,926)
Beginning Balance at Mar. 31, 2020	2,663,441			55,057		1,073,089		1,646,751			219,390		(330,846)
Total comprehensive income (loss)	125,401							60,529			64,872
Dividends	(14,991)							(14,991)
Purchase of treasury stock	(73)					5,115							(5,188)
Forfeitures of equity awards, net of issuances						155							(155)
Recognition of equity-based compensation	3,292					3,292
Sale of treasury stock	137					25							112
Exercise of stock options	188					37							151
Ending Balance at Jun. 30, 2020	2,777,395			55,057		1,081,713		1,692,289			284,262		(335,926)
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)	84,822							180,055			(95,233)
Dividends	(31,167)							(31,167)
Purchase of treasury stock	(4,088)												(4,088)
Forfeitures of equity awards, net of issuances	695					(4,122)							4,817
Recognition of equity-based compensation	8,609					8,609
Sale of treasury stock	301					148							153
Exercise of stock options	14,124					3,054							11,070
Ending Balance at Jun. 30, 2021	3,090,244			55,057		1,098,139		2,040,134			223,107		(326,193)
Beginning Balance at Mar. 31, 2021	2,958,239			55,057		1,093,667		1,968,318			169,197		(328,000)
Total comprehensive income (loss)	141,322							87,412			53,910
Dividends	(15,596)							(15,596)
Purchase of treasury stock	(61)												(61)
Forfeitures of equity awards, net of issuances						(79)							79
Recognition of equity-based compensation	4,152					4,152
Sale of treasury stock	150					83							67
Exercise of stock options	2,038					316							1,722
Ending Balance at Jun. 30, 2021	$ 3,090,244			$ 55,057		$ 1,098,139		$ 2,040,134			$ 223,107		$ (326,193)