Stock-Based Compensation Plans - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Beginning balance	575,564	529,611	855,740
Number of Shares, Granted	82,474	168,217	54,838
Number of Shares, Canceled	(548)	(1,676)
Number of Shares, Exercised	(106,899)	(120,588)	(380,967)
Number of Shares, Ending Balance	550,591	575,564	529,611
Number of Shares, Exercisable	171,782
Weighted Average Exercise Price, Beginning Balance	$ 132.93	$ 67.60	$ 36.80
Weighted Average Exercise Price, Granted	279.57	261.19	156.85
Weighted Average Exercise Price, Canceled	198.67	142.69
Weighted Average Exercise Price, Exercised	28.24	24.66	11.26
Weighted Average Exercise Price, Ending Balance	175.16	$ 132.93	$ 67.60
Weighted Average Exercise Price, Exercisable	$ 96.71
Remaining Contractual Term, Outstanding at December 31, 2019	2 years 9 months 18 days
Remaining Contractual Term, Exercisable at December 31, 2019	1 year 6 months
Intrinsic Value, Exercised	$ 33,639
Intrinsic Value, Ending Balance	112,294
Intrinsic Value, Exercisable	$ 48,512