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- Definition

Share based compensation arrangement by share based payment award award contractual term.

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- Definition

Share-based compensation arrangement by share-based payment award, granted rights, percentage.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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- Definition

Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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.

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- Definition

Date the equity-based award expires, in CCYY-MM-DD format.

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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.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Gross number of share options (or share units) granted during the period.

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Equity Incentive Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of awards granted	1,121,000	1,104,000	931,000
Weighted average grant date fair value of award granted	$ 3.20	$ 7.31	$ 6.78
Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted (in shares)	0	0
Share-based compensation expenses	$ 0	$ 100,000	$ 400,000
Employee Stock Options \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	1 year
Employee Stock Options \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	4 years
Restricted Stock And Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance-based restricted stock and restricted stock units, eliminated minimum vesting period under amended 2004 plan	3 years
Share-based compensation expenses	$ 5,800,000	6,000,000	4,600,000
Total unrecognized compensation expense related to grants of restricted stock and restricted stock units	$ 4,200,000
Weighted average period for unrecognized compensation expense related to grants of stock options	1 year 8 months 12 days
Shares vested related to grants of restricted stock and restricted stock units	$ 5,200,000	$ 6,000,000	4,200,000
Performance Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Share-based compensation expenses			$ 0
Performance period to grant award	1 year
Number of awards granted	0	0	608,500
Weighted average grant date fair value of award granted			$ 6.75
Performance Restricted Stock Units \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share award grant percentage	0.00%
Performance Restricted Stock Units \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share award grant percentage	200.00%
2000 Plan \| Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term of stock options	ten years
2000 Plan \| Employee Stock Options \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	4 years
2000 Plan \| Employee Stock Options \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	5 years
2000 Plan \| Class A common stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized under 2000 plan and 2004 plan	11,500,000
2004 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation award extended expiration date	May 29, 2024
2004 Plan \| Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term of stock options	ten years
Vesting period	4 years
2004 Plan \| Class A common stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized under 2000 plan and 2004 plan	10,000,000