Equity Incentive Plans - Additional Information (Detail) - USD ($)
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12 Months Ended |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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|
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| Total unrecognized compensation expense employee stock option plans |
$ 200,000
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|
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| Number of awards granted |
931,000
|
764,000
|
1,181,000
|
| Weighted average grant date fair value of award granted |
$ 6.78
|
$ 8.25
|
$ 4.51
|
| Minimum |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Vesting period |
1 year
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| Maximum |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Vesting period |
4 years
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| Employee Stock Options |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Share-based compensation expenses |
$ 400,000
|
$ 1,500,000
|
$ 2,300,000
|
| Weighted average period for unrecognized compensation expense related to grants of stock options |
1 year 3 months 18 days
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| Restricted Stock And Restricted Stock Units |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Performance-based restricted stock and restricted stock units, eliminated minimum vesting period under amended 2004 plan |
3 years
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| Share-based compensation expenses |
$ 4,600,000
|
3,800,000
|
2,100,000
|
| Weighted average period for unrecognized compensation expense related to grants of stock options |
1 year 9 months 18 days
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|
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| Total unrecognized compensation expense related to grants of restricted stock and restricted stock units |
$ 5,400,000
|
|
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| Shares vested related to grants of restricted stock and restricted stock units |
$ 4,200,000
|
3,500,000
|
$ 1,600,000
|
| Performance Restricted Stock Units |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Vesting period |
3 years
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| Share-based compensation expenses |
$ 0
|
$ 0
|
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| Performance period to grant award |
1 year
|
|
|
| Number of awards granted |
608,500
|
447,000
|
|
| Weighted average grant date fair value of award granted |
$ 6.75
|
$ 8.39
|
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| Performance Restricted Stock Units | Minimum |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Share award grant percentage |
0.00%
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| Performance Restricted Stock Units | Maximum |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Share award grant percentage |
200.00%
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| 2000 Plan | Employee Stock Options |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Contractual term of stock options |
10 years
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| 2000 Plan | Employee Stock Options | Minimum |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Vesting period |
4 years
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| 2000 Plan | Employee Stock Options | Maximum |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Vesting period |
5 years
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| 2000 Plan | Class A common stock |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Common stock shares authorized under 2000 plan and 2004 plan |
11,500,000
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| 2004 Plan |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Share-based compensation award extended expiration date |
May 29, 2024
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| 2004 Plan | Employee Stock Options |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Contractual term of stock options |
10 years
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| Vesting period |
4 years
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| 2004 Plan | Class A common stock |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Common stock shares authorized under 2000 plan and 2004 plan |
10,000,000
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