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	305,548
Other comprehensive loss, net of tax	(609,510)
Stockholders' Equity ending balance at Jun. 30, 2020	2,966,434	126	2,690,966	5,018,277	(1,581,975)	(3,160,960)
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)
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	380,486
Other comprehensive loss, net of tax	97,981
Stockholders' Equity ending balance at Jun. 30, 2021	3,488,847	127	2,821,453	5,797,431	(1,265,177)	(3,864,987)
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)