Consolidated Statements Of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Shareholders' equity (shares) at Dec. 31, 2018		277,110
Shareholders' equity at Dec. 31, 2018	$ 4,817,782	$ 2,771	$ 3,201,427	$ (345)	$ 1,613,929
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (shares)		434
Stock option exercises	5,209	$ 4	5,205
Stock issuances (shares)		974
Share issuances	5,800	$ 10	5,790
Dividends declared	(61,463)				(61,463)
Share repurchases (shares)		(3,543)
Share repurchases	(108,471)	$ (35)			(108,436)
Cash paid for shares withheld for taxes	(10,350)				(10,350)
Share-based compensation	13,452		13,452
Net income	407,798				407,798
Other comprehensive income	50			50
Shareholders' equity (shares) at Jun. 30, 2019		274,975
Shareholders' equity at Jun. 30, 2019	5,069,807	$ 2,750	3,225,874	(295)	1,841,478
Shareholders' equity (shares) at Mar. 31, 2019		277,256
Shareholders' equity at Mar. 31, 2019	4,933,439	$ 2,771	3,216,473	(320)	1,714,515
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (shares)		316
Stock option exercises	3,764	$ 3	3,761
Stock issuances (shares)		26
Share issuances	0	$ 2	(2)
Dividends declared	(30,633)				(30,633)
Share repurchases (shares)		(2,623)
Share repurchases	(83,471)	$ (26)			(83,445)
Cash paid for shares withheld for taxes	0				0
Share-based compensation	5,642		5,642
Net income	241,041				241,041
Other comprehensive income	25			25
Shareholders' equity (shares) at Jun. 30, 2019		274,975
Shareholders' equity at Jun. 30, 2019	5,069,807	$ 2,750	3,225,874	(295)	1,841,478
Shareholders' equity (shares) at Dec. 31, 2019		270,235
Shareholders' equity at Dec. 31, 2019	5,458,180	$ 2,702	3,235,149	(245)	2,220,574
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	(735)				(735)
Stock option exercises (shares)		13
Stock option exercises	99	$ 0	99
Stock issuances (shares)		755
Share issuances	4,096	$ 8	4,088
Dividends declared	(65,056)				(65,056)
Share repurchases (shares)		(2,825)
Share repurchases	(95,676)	$ (28)			(95,648)
Cash paid for shares withheld for taxes	(14,853)				(14,853)
Share-based compensation	13,232		13,232
Net income	552,331				552,331
Other comprehensive income	50			50
Shareholders' equity (shares) at Jun. 30, 2020		268,178
Shareholders' equity at Jun. 30, 2020	5,851,668	$ 2,682	3,252,568	(195)	2,596,613
Shareholders' equity (shares) at Mar. 31, 2020		268,149
Shareholders' equity at Mar. 31, 2020	5,530,391	$ 2,681	3,247,475	(220)	2,280,455
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (shares)		6
Stock option exercises	48	$ 0	48
Stock issuances (shares)		23
Share issuances	1	$ 1	0
Dividends declared	(32,447)				(32,447)
Cash paid for shares withheld for taxes	(15)				(15)
Share-based compensation	5,045		5,045
Net income	348,620				348,620
Other comprehensive income	25			25
Shareholders' equity (shares) at Jun. 30, 2020		268,178
Shareholders' equity at Jun. 30, 2020	$ 5,851,668	$ 2,682	$ 3,252,568	$ (195)	$ 2,596,613

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