Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans - 2013 Omnibus Equity Incentive Plan - Award Limitations - Additional Information (Detail)

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Stock-Based Compensation Plans - 2013 Omnibus Equity Incentive Plan - Award Limitations - Additional Information (Detail)
12 Months Ended
Dec. 31, 2017
Incentive_Plan
shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Common stock shares reserved for issuance of awards 5,500,000
Common stock shares available for grant 5,586,917
Increase of common stock share reserve approved 3,300,000
Number of active equity plans | Incentive_Plan 1
Equity incentive plan amendment, shareholder approval date May 04, 2017
Equity incentive plan amendment, board of directors approval date 2017-02