Soft Dollar Arrangements - Additional Information (Detail) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
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| Soft Dollar Arrangements [Abstract] | ||||
| Soft dollar credits | $ 193 | $ 178 | $ 386 | $ 356 |
| X | ||||||||||
- Definition Soft dollar arrangements. No definition available.
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| X | ||||||||||
- Definition Soft dollar credits. No definition available.
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