Stock-based Compensation - Company's Options Outstanding (Detail)	12 Months Ended
	Dec. 31, 2016 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding - Number of Shares (in shares)	4,721,941
Options Exercisable - Number of Shares (in shares)	2,666,260
$0.00 – $1.92
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum (in dollars per share) | $ / shares	$ 0
Exercise Price, Maximum (in dollars per share) | $ / shares	$ 1.92
Options Outstanding - Number of Shares (in shares)	520,391
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	5 years 2 months 16 days
Options Exercisable - Number of Shares (in shares)	520,391
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	5 years 2 months 16 days
$2.24 – $6.72
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum (in dollars per share) | $ / shares	$ 2.24
Exercise Price, Maximum (in dollars per share) | $ / shares	$ 6.72
Options Outstanding - Number of Shares (in shares)	589,559
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	4 years 7 months 21 days
Options Exercisable - Number of Shares (in shares)	584,346
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	4 years 7 months 17 days
$8.96 – $12.60
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum (in dollars per share) | $ / shares	$ 8.96
Exercise Price, Maximum (in dollars per share) | $ / shares	$ 12.60
Options Outstanding - Number of Shares (in shares)	510,578
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	7 years 6 months 29 days
Options Exercisable - Number of Shares (in shares)	316,203
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	7 years 2 months 23 days
$12.77
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum (in dollars per share) | $ / shares	$ 12.77
Exercise Price, Maximum (in dollars per share) | $ / shares	$ 12.77
Options Outstanding - Number of Shares (in shares)	754,288
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	8 years 1 month 13 days
Options Exercisable - Number of Shares (in shares)	320,425
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	8 years 1 month 13 days
$12.94
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum (in dollars per share) | $ / shares	$ 12.94
Exercise Price, Maximum (in dollars per share) | $ / shares	$ 12.94
Options Outstanding - Number of Shares (in shares)	654,721
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	9 years 1 month 6 days
Options Exercisable - Number of Shares (in shares)	126,423
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	9 years 1 month 6 days
$13.58 – $14.95
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum (in dollars per share) | $ / shares	$ 13.58
Exercise Price, Maximum (in dollars per share) | $ / shares	$ 14.95
Options Outstanding - Number of Shares (in shares)	365,131
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	8 years 7 months 2 days
Options Exercisable - Number of Shares (in shares)	108,188
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	7 years 11 months 12 days
$15.12 – $17.50
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum (in dollars per share) | $ / shares	$ 15.12
Exercise Price, Maximum (in dollars per share) | $ / shares	$ 17.50
Options Outstanding - Number of Shares (in shares)	364,479
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	8 years 7 months 21 days
Options Exercisable - Number of Shares (in shares)	114,588
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	8 years 4 days
$18.18 – $18.90
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum (in dollars per share) | $ / shares	$ 18.18
Exercise Price, Maximum (in dollars per share) | $ / shares	$ 18.90
Options Outstanding - Number of Shares (in shares)	736,894
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	7 years 1 month 2 days
Options Exercisable - Number of Shares (in shares)	533,742
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	7 years 1 month 2 days
$19.45 – $22.71
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum (in dollars per share) | $ / shares	$ 19.45
Exercise Price, Maximum (in dollars per share) | $ / shares	$ 22.71
Options Outstanding - Number of Shares (in shares)	225,900
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	9 years 2 months 1 day
Options Exercisable - Number of Shares (in shares)	41,954
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	7 years 3 months 29 days