Unaudited Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Stockholders' Equity beginning balance at Dec. 31, 2019	$ 3,711,616	$ 124	$ 2,494,721	$ 4,712,729	$ (972,465)	$ (2,523,493)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	147,060			147,060
Other comprehensive loss, net of tax	(619,659)				(619,659)
Acquisition of common stock	(530,237)		75,000			(605,237)
Share-based compensation	14,175		14,175
Issuance of common stock	73,274	1	73,273
Stockholders' Equity ending balance at Mar. 31, 2020	2,796,229	125	2,657,169	4,859,789	(1,592,124)	(3,128,730)
Stockholders' Equity beginning balance at Dec. 31, 2019	3,711,616	124	2,494,721	4,712,729	(972,465)	(2,523,493)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	494,365
Other comprehensive loss, net of tax	(610,671)
Stockholders' Equity ending balance at Sep. 30, 2020	2,937,750	126	2,713,022	5,207,094	(1,583,136)	(3,399,356)
Stockholders' Equity beginning balance at Mar. 31, 2020	2,796,229	125	2,657,169	4,859,789	(1,592,124)	(3,128,730)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	158,488			158,488
Other comprehensive loss, net of tax	10,149				10,149
Acquisition of common stock	(32,230)					(32,230)
Share-based compensation	8,989		8,989
Issuance of common stock	24,809	1	24,808
Stockholders' Equity ending balance at Jun. 30, 2020	2,966,434	126	2,690,966	5,018,277	(1,581,975)	(3,160,960)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	188,817			188,817
Other comprehensive loss, net of tax	(1,161)				(1,161)
Acquisition of common stock	(238,396)					(238,396)
Share-based compensation	11,905		11,905
Issuance of common stock	10,151		10,151
Stockholders' Equity ending balance at Sep. 30, 2020	2,937,750	126	2,713,022	5,207,094	(1,583,136)	(3,399,356)
Stockholders' Equity beginning balance at Dec. 31, 2020	3,355,411	126	2,749,900	5,416,945	(1,363,158)	(3,448,402)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	184,239			184,239
Other comprehensive loss, net of tax	(117,861)				(117,861)
Acquisition of common stock	(170,382)					(170,382)
Share-based compensation	17,747		17,747
Issuance of common stock	27,345	1	27,344
Stockholders' Equity ending balance at Mar. 31, 2021	3,296,499	127	2,794,991	5,601,184	(1,481,019)	(3,618,784)
Stockholders' Equity beginning balance at Dec. 31, 2020	3,355,411	126	2,749,900	5,416,945	(1,363,158)	(3,448,402)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	614,493
Other comprehensive loss, net of tax	(72,886)
Stockholders' Equity ending balance at Sep. 30, 2021	3,174,985	127	2,850,143	6,031,438	(1,436,044)	(4,270,679)
Stockholders' Equity beginning balance at Mar. 31, 2021	3,296,499	127	2,794,991	5,601,184	(1,481,019)	(3,618,784)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	196,247			196,247
Other comprehensive loss, net of tax	215,842				215,842
Acquisition of common stock	(246,203)					(246,203)
Share-based compensation	17,885		17,885
Issuance of common stock	8,577		8,577
Stockholders' Equity ending balance at Jun. 30, 2021	3,488,847	127	2,821,453	5,797,431	(1,265,177)	(3,864,987)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	234,007			234,007
Other comprehensive loss, net of tax	(170,867)				(170,867)
Acquisition of common stock	(405,692)					(405,692)
Share-based compensation	16,453		16,453
Issuance of common stock	12,237		12,237
Stockholders' Equity ending balance at Sep. 30, 2021	$ 3,174,985	$ 127	$ 2,850,143	$ 6,031,438	$ (1,436,044)	$ (4,270,679)