Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Commitments and Contingencies Disclosure [Abstract] | |||
| Operating leases initial non-cancelable lease term | 1 year | ||
| Rental expenses | $ 7.0 | $ 6.6 | $ 7.6 |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line. No definition available.
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| X | ||||||||||
- Definition Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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