CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings Cumulative-effect adjustment	Retained Earnings	Accumulated other comprehensive Income (loss)	Treasury Stock	Cumulative-effect adjustment	Total
Balance, beginning at Dec. 31, 2018	$ 1,397	$ 2,495,853		$ 291,919	$ (132,195)	$ (132,135)		$ 2,524,839
Balance (in shares) at Dec. 31, 2018	134,874,302
Increase (Decrease) in Stockholders' Equity
Net income				216,556				216,556
Cash dividends declared				(104,392)				(104,392)
Equity-based awards	$ 2	5,471		(766)		(1,764)		2,943
Equity-based awards (in shares)	185,736
Common stock repurchased						(98,809)		(98,809)
Common stock repurchased (in shares)	(3,799,138)
Other comprehensive income, net of tax					113,421			113,421
Balance, ending at Sep. 30, 2019	$ 1,399	2,501,324		403,317	(18,774)	(232,708)		2,654,558
Balance (in shares) at Sep. 30, 2019	131,260,900
Balance, beginning at Jun. 30, 2019	$ 1,399	2,499,946		363,748	(31,984)	(173,668)		2,659,441
Balance (in shares) at Jun. 30, 2019	133,508,212
Increase (Decrease) in Stockholders' Equity
Net income				74,199				74,199
Cash dividends declared				(34,408)				(34,408)
Equity-based awards		1,378		(222)		(231)		925
Equity-based awards (in shares)	41,980
Common stock repurchased						(58,809)		(58,809)
Common stock repurchased (in shares)	(2,289,292)
Other comprehensive income, net of tax					13,210			13,210
Balance, ending at Sep. 30, 2019	$ 1,399	2,501,324		403,317	(18,774)	(232,708)		2,654,558
Balance (in shares) at Sep. 30, 2019	131,260,900
Increase (Decrease) in Stockholders' Equity
Cumulative-effect adjustment of change in accounting principle, net of tax: ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments			$ (12,517)				$ (12,517)
Balance, beginning at Dec. 31, 2019	$ 1,399	2,503,677		437,072	(31,749)	(270,141)		$ 2,640,258
Balance (in shares) at Dec. 31, 2019	129,928,479							129,928,479
Increase (Decrease) in Stockholders' Equity
Net income				124,015				$ 124,015
Cash dividends declared				(101,322)				(101,322)
Equity-based awards	$ 3	8,172		(933)		(1,745)		5,497
Equity-based awards (in shares)	201,069
Common stock repurchased						(5,000)		(5,000)
Common stock repurchased (in shares)	(217,759)
Other comprehensive income, net of tax					83,003			83,003
Balance, ending at Sep. 30, 2020	$ 1,402	2,511,849		446,315	51,254	(276,886)		$ 2,733,934
Balance (in shares) at Sep. 30, 2020	129,911,789							129,911,789
Balance, beginning at Jun. 30, 2020	$ 1,401	2,509,271		415,296	52,731	(276,802)		$ 2,701,897
Balance (in shares) at Jun. 30, 2020	129,866,898
Increase (Decrease) in Stockholders' Equity
Net income				65,101				65,101
Cash dividends declared				(33,775)				(33,775)
Equity-based awards	$ 1	2,578		(307)		(84)		2,188
Equity-based awards (in shares)	44,891
Other comprehensive income, net of tax					(1,477)			(1,477)
Balance, ending at Sep. 30, 2020	$ 1,402	$ 2,511,849		$ 446,315	$ 51,254	$ (276,886)		$ 2,733,934
Balance (in shares) at Sep. 30, 2020	129,911,789							129,911,789