Stock-Based Compensation - Summary of Option Activity for 2006 Plan and the 2016 Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Number of Shares
Expired (in shares)	(10,104)
Weighted Average Exercise Price at Grant Date
Expired (in dollars per share)	$ 11.78
2006 Plan and 2016 Plan
Number of Shares
Beginning balance (in shares)	4,495,145
Granted (in shares)	487,500
Forfeited (in shares)	(225,000)
Exercised (in shares)	(172,500)
Ending balance (in shares)	4,575,041	4,495,145
Exercisable (in shares)	3,379,139
Vested and expected to vest at end of period (in shares)	4,340,916
Weighted Average Exercise Price at Grant Date
Beginning balance (in dollars per share)	$ 12.21
Granted (in dollars per share)	11.42
Forfeited (in dollars per share)	18.83
Exercised (in dollars per share)	4.96
Ending balance (in dollars per share)	12.07	$ 12.21
Exercisable (in dollars per share)	11.02
Vested and expected to vest at end of period (in dollars per share)	$ 11.99
Weighted Average Remaining Term (Years)
Weighted Average Remaining Term	5 years 9 months 21 days	5 years 6 months 29 days
Exercisable	4 years 7 months 17 days
Vested and expected to vest at end of period	5 years 7 months 6 days
Aggregate Intrinsic Value
Beginning balance	$ 21,148
Exercised	890
Ending balance	4,818	$ 21,148
Exercisable	4,818
Vested and expected to vest at end of period	$ 4,818

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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- 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.