Retirement Savings Plan - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Employees' contributions at a rate	3.00%
Matching Contribution Percentage	50.00%
Employees' contributions at a rate	2.00%
Matching Contribution Amount	$ 2.8	$ 2.5	$ 2.0
Matching Contribution Percentage	100.00%

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Amount of discretionary contributions made by an employer to a defined contribution plan.

No definition available.

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Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

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Defined contribution plan employer match percentage up to 3% of employee compensation.

No definition available.

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Defined Contribution Plan Maximum Employer Match Percentage For First Compensation Slab

No definition available.

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Defined Contribution Plan Maximum Employer Match Percentage For Next Compensation Slab

No definition available.

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