Stock-Based Compensation - Additional Information (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares) | shares	2,400,000
Common stock available for issuance (in shares) | shares	297,407
Stock-based compensation expense	$ 23,116	$ 20,288	$ 11,948
Weighted-average remaining contractual term, stock options outstanding	6 months	1 year 2 months 24 days
Weighted-average remaining contractual term, stock options vested and exercisable	6 months
Aggregate intrinsic value, stock options outstanding	$ 0
Aggregate intrinsic value, stock options vested and exercisable	5,100
Stock options vested (in shares) | shares		0
Intrinsic value, stock options exercised	3,000	$ 2,500	1,300
Cash received from stock option exercises	819	$ 111	$ 491
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant-date intrinsic value	$ 26,000
Weighted-average grant-date fair value (in $ per share) | $ / shares	$ 131.16	$ 108.32	$ 80.33
Fair value of awards vested	$ 12,500	$ 11,300	$ 9,300
Share settlement under RSUs (in shares) | shares	41,101	32,716	37,488
Cash used for employee withholding tax payments	$ 5,300	$ 3,500	$ 1,500
Unamortized stock-based compensation expense	$ 32,200	$ 29,300
Weighted average remaining amortization period	1 year 5 months 24 days	1 year 6 months 24 days
Restricted stock units (RSUs), performance-based
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares) | shares	68,803	122,606
Period for recognition of compensation expense		3 years
Stock-based compensation expense	$ 8,200	$ 7,800
Unamortized stock-based compensation expense	$ 11,400	$ 10,900
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life in years	10 years
Vesting period of stock options in years	3 years
Minimum | Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life in years	1 year
Maximum | Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life in years	3 years
Common Stock | Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio	1