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Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions |  | 12 Months Ended
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Approximate number of shares employees purchased under the Employee Stock Purchase Plan |  | 874,235 |  |
2014 Stock Incentive Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Total aggregate number of shares of common stock that may be issued | 12,840,000 | 12,840,000 |  |
Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Compensation cost recognition period for unvested awards | 1 year 6 months |  |  |
Unrecognized compensation cost related to unvested awards | $ 1.6 | $ 1.6 | $ 1.8 | $ 1.2
Vesting period |  | 3 years |  |
Number of shares or rights issued |  | 80,570 | 86,614 | 89,850
Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] | Share-Based Compensation Award, Tranche One [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock-based Compensation vesting percentage |  | 33.33% |  |
Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] | Share-Based Compensation Award, Tranche Two [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock-based Compensation vesting percentage |  | 33.33% |  |
Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] | Share-Based Compensation Award, Tranche Three [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock-based Compensation vesting percentage |  | 33.33% |  |
Stock Appreciation Rights [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Unrecognized compensation cost related to unvested awards | 0.4 | $ 0.4 |  |
Maximum contractual term |  | 10 years |  |
Fair value assumptions method used |  | Black-Scholes option-pricing model |  |
Number of shares or rights issued |  |  |  | 0
Weighted-average fair value of grants |  | $ 22.09 | $ 13.99 |
Time-Based Restricted Stock and Time-Based Restricted Stock Units [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Compensation cost recognition period for unvested awards |  | 2 years 8 months 12 days |  |
Unrecognized compensation cost related to unvested awards | $ 5.1 | $ 5.1 |  |
Total fair value of restricted shares vested |  | $ 4.2 | $ 5.5 | $ 1.7
Number of shares or rights issued |  | 87,264 | 72,402 | 115,748
Employee Stock Purchase Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Total aggregate number of shares of common stock that may be issued | 1,200,000 | 1,200,000 |  |
Percentage of market price on lesser of either first day of calendar quarter or last day of calendar quarter for purchase price |  | 85.00% |  |
Percentage of gross compensation eligible employees may elect to participate in the plan | 15.00% | 15.00% |  |
Minimum [Member] | Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Percentage of target number of shares that will vest |  | 0.00% |  |
Maximum [Member] | Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Percentage of target number of shares that will vest |  | 200.00% |  |

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- Definition Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition For each plan, identification of the award pricing model or other valuation method used in calculating the weighted average fair values disclosed. The model is also used to calculate the compensation expense that is shown within the balance sheet, income statement, and cash flow. Examples of valuation techniques are lattice models (binomial model), closed-form models (Black-Scholes-Merton formula), and a Monte Carlo simulation technique. Fair value is the amount at which an asset or liability could be bought or incurred or sold or settled in a current transaction between willing parties, that is, other than in a forced or liquidation sale. May include disclosures about the assumptions underlying application of the method selected. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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