Shareholders' Equity - Summary of Changes in Shareholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 2,612,412	$ 2,119,439	$ 2,341,244	$ 1,808,562
Net income	256,466	223,787	596,244	622,402
Deferred Compensation Activity Adjustments			0	0
Treasury Stock, Value, Acquired, Cost Method		(61,063)	(216,582)	(365,542)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition		20,770	35,565	58,680
APIC, Share-based Payment Arrangement, Option, Increase for Cost Recognition	13,639
APIC, Share-based Payment Arrangement, Recognition and Exercise	36,476	68,524	162,522	247,355
Stock Issued During Period, Value, Stock Options Exercised	0	0	0	0
Ending Balance	2,918,993	2,371,457	2,918,993	2,371,457
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	206	206	206	206
Ending Balance	206	206	206	206
Additional Paid-In-Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	2,151,623	1,962,156	2,055,407	1,820,223
APIC, Share-based Payment Arrangement, Increase for Cost Recognition		20,770	35,565	58,680
APIC, Share-based Payment Arrangement, Option, Increase for Cost Recognition	13,639
APIC, Share-based Payment Arrangement, Recognition and Exercise	36,476	68,524	162,522	247,355
Stock Issued During Period, Value, Stock Options Exercised	(13,531)	(31,270)	(65,287)	(106,078)
Ending Balance	2,188,207	2,020,180	2,188,207	2,020,180
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	8,249,650	7,429,948	7,909,872	7,031,333
Net income	256,466	223,787	596,244	622,402
Ending Balance	8,506,116	7,653,735	8,506,116	7,653,735
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(7,789,067)	(7,272,871)	(7,624,241)	(7,043,200)
Treasury Stock, Value, Acquired, Cost Method		(61,063)	(216,582)	(365,542)
Stock Issued During Period, Value, Stock Options Exercised	13,531	31,270	65,287	106,078
Ending Balance	(7,775,536)	(7,302,664)	(7,775,536)	(7,302,664)
Deferred Compensation Trust [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(16,710)	(16,912)	(16,912)	(16,937)
Deferred Compensation Activity Adjustments			202	25
Ending Balance	(16,710)	(16,912)	(16,710)	(16,912)
Deferred Compensation Liability [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	16,710	16,912	16,912	16,937
Deferred Compensation Activity Adjustments			(202)	(25)
Ending Balance	$ 16,710	$ 16,912	$ 16,710	$ 16,912