Equity-Based Compensation - Schedule of Activity Related to Stock Option Awards (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options, Outstanding, Beginning Balance \| shares	2,923,448
Options, Forfeited \| shares	(429,992)
Options, Expired \| shares	(1,493,902)
Options, Exercised \| shares	(234,977)
Options, Outstanding, Ending Balance \| shares	764,577
Options, Exercisable at December 31, 2018 \| shares	435,825
Weighted Average Exercise Price, Outstanding, Beginning Balance \| $ / shares	$ 18.78
Weighted Average Exercise Price, Forfeited \| $ / shares	18.00
Weighted Average Exercise Price, Expired \| $ / shares	19.46
Weighted Average Exercise Price, Exercised \| $ / shares	18.23
Weighted Average Exercise Price, Outstanding, Ending Balance \| $ / shares	18.05
Weighted Average Exercise Price, Exercisable at December 31, 2018 \| $ / shares	$ 18.16
Weighted Average Remaining Contractual Life, Outstanding at December 31, 2018	6 years 9 months 25 days
Weighted Average Remaining Contractual Life, Exercisable at December 31, 2018	6 years 8 months 19 days
Aggregate Intrinsic Value, Outstanding at December 31, 2018 \| $	$ 3,087
Aggregate Intrinsic Value, Exercisable at December 31, 2018 \| $	$ 1,711

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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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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.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of non-vested options forfeited.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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