Shareholders' Equity - Summary of Changes in Shareholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1,605,492
Cumulative-effect adjustment from adoption of ASU 2014-09, net of tax			$ 2,196
Net income	166,049	$ 102,923
Purchase of common stock for treasury	(357,242)
Equity-based compensation	9,509
Proceeds from stock options exercised	40,804
Ending Balance	1,466,808
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	206
Ending Balance	206
Additional Paid-In-Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	1,644,197
Equity-based compensation	9,509
Proceeds from stock options exercised	40,804
Treasury stock issued upon option exercise and restricted share vesting	(16,410)
Ending Balance	1,678,100
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	6,231,940
Cumulative-effect adjustment from adoption of ASU 2014-09, net of tax			$ 2,196
Net income	166,049
Ending Balance	6,400,185
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(6,270,851)
Purchase of common stock for treasury	357,242
Treasury stock issued upon option exercise and restricted share vesting	16,410
Ending Balance	(6,611,683)
Deferred Compensation Trust [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(17,383)
Deferred compensation activity	(6)
Ending Balance	(17,389)
Deferred Compensation Liability [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	17,383
Deferred compensation activity	6
Ending Balance	$ 17,389