Shareholders' Equity - Summary of Changes in Shareholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 1,304,441
Cumulative-effect adjustment from adoption of ASU 2016-09, net of tax	$ 609		609
Net income	147,877	$ 91,676	250,800	$ 156,979
Purchase of common stock for treasury			(159,506)
Equity-based compensation			21,467
Proceeds from stock options exercised			117,966
Ending Balance	1,535,777		1,535,777
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			206
Ending Balance	206		206
Additional Paid-In-Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			1,515,828
Cumulative-effect adjustment from adoption of ASU 2016-09, net of tax	1,566		1,566
Equity-based compensation			21,467
Proceeds from stock options exercised			117,966
Treasury stock issued upon option exercise and restricted share vesting			(48,869)
Ending Balance	1,607,958		1,607,958
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			5,695,376
Cumulative-effect adjustment from adoption of ASU 2016-09, net of tax	(957)		(957)
Net income			250,800
Ending Balance	5,945,219		5,945,219
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(5,906,969)
Purchase of common stock for treasury			(159,506)
Treasury stock issued upon option exercise and restricted share vesting			48,869
Ending Balance	(6,017,606)		(6,017,606)
Deferred Compensation Trust [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(17,375)
Deferred compensation activity			4
Ending Balance	(17,371)		(17,371)
Deferred Compensation Liability [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			17,375
Deferred compensation activity			(4)
Ending Balance	$ 17,371		$ 17,371