Shareholders' Equity - Summary of Changes in Shareholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 2,416,919	$ 1,898,776	$ 2,341,244	$ 1,808,562
Net income	164,075	210,209	339,778	398,615
Deferred Compensation Activity Adjustments	0		0	0
Treasury Stock, Value, Acquired, Cost Method		(87,980)	(216,582)	(304,479)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition		18,577	21,926	37,910
APIC, Share-based Payment Arrangement, Option, Increase for Cost Recognition	14,434
APIC, Share-based Payment Arrangement, Recognition and Exercise	16,984	79,857	126,046	178,831
Stock Issued During Period, Value, Stock Options Exercised	0	0	0	0
Ending Balance	2,612,412	2,119,439	2,612,412	2,119,439
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	2,127,315	1,899,100	2,055,407	1,820,223
APIC, Share-based Payment Arrangement, Increase for Cost Recognition		18,577	21,926	37,910
APIC, Share-based Payment Arrangement, Option, Increase for Cost Recognition	14,434
APIC, Share-based Payment Arrangement, Recognition and Exercise	16,984	79,857	126,046	178,831
Stock Issued During Period, Value, Stock Options Exercised	(7,110)	(35,378)	(51,756)	(74,808)
Ending Balance	2,151,623	1,962,156	2,151,623	1,962,156
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	8,085,575	7,219,739	7,909,872	7,031,333
Net income	164,075	210,209	339,778	398,615
Ending Balance	8,249,650	7,429,948	8,249,650	7,429,948
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(7,796,177)	(7,220,269)	(7,624,241)	(7,043,200)
Treasury Stock, Value, Acquired, Cost Method		(87,980)	(216,582)	(304,479)
Stock Issued During Period, Value, Stock Options Exercised	7,110	35,378	51,756	74,808
Ending Balance	(7,789,067)	(7,272,871)	(7,789,067)	(7,272,871)
Deferred Compensation Trust [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(16,912)	(16,912)	(16,912)	(16,937)
Deferred Compensation Activity Adjustments	202		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	16,912	16,912	16,912	16,937
Deferred Compensation Activity Adjustments	(202)		(202)	(25)
Ending Balance	$ 16,710	$ 16,912	$ 16,710	$ 16,912