Benefit Plans - Defined Contribution Plan (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Retirement Benefits [Abstract] | |||
| Defined Contribution expense | $ 12,585 | $ 13,103 | $ 6,864 |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of cost for defined contribution plan. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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