Stock-Based Compensation - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Options
Beginning balance (in shares)	466,677
Granted (in shares)	132,155
Exercised (in shares)	(468)
Canceled (in shares)	(3,148)
Ending balance (in shares)	595,216	466,677
Exercisable at period end (in shares)	388,634
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 61.04
Granted (in dollars per share)	70.46
Exercised (in dollars per share)	64.54
Canceled (in dollars per share)	73.34
Ending balance (in dollars per share)	63.08	$ 61.04
Exercisable (in dollars per share)	$ 54.89
Weighted Average Remaining Contractual Life
Outstanding, weighted average remaining contractual life (in years)	6 years 2 months 12 days	5 years 8 months 12 days
Exercisable weighted average remaining contractual life (in years)	5 years 2 months 12 days
Aggregate Intrinsic Value
Beginning balance	$ 5,003
Granted	172
Exercised	(19)
Canceled	0
Ending balance	5,168	$ 5,003
Exercisable	$ 6,558

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.