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Stock Incentive Plans and Stock Purchase Plan - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
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3 Months Ended |
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Mar. 31, 2015
|
Mar. 31, 2014
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Shares available for future grants and awards under Stock Incentive Plans |
6,300,000 |
|
| Stock-based compensation expense |
$ 7.8 |
$ 8.1 |
| Excess tax benefit related to employee stock incentive plans |
$ 1.1 |
|
| Stock Option [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
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| Number of years over which stock awards vest or become exercisable |
3 years |
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| Stock Option [Member] | Maximum [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
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| Vesting period of options, maximum years |
10 years |
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| Restricted Stock [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
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| Number of years over which stock awards vest or become exercisable |
3 years |
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| 1996 Non-Qualified Employee Stock Purchase Plan [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Percentage of market value of common stock at which employees are permitted to purchase |
85.00% |
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| Percentage of discount received by participating employees |
15.00% |
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| Shares reserved for issuance |
283,400 |
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| Shares issued under Stock Purchase Plan |
51,138 |
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