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v3.10.0.1

Income Taxes - Periods Open to Tax Examination (Details) | 12 Months Ended
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Dec. 31, 2018
Minimum |
Income Tax Contingency [Line Items] |
Number of tax years open for state tax audit (in years) | 3 years
Maximum |
Income Tax Contingency [Line Items] |
Number of tax years open for state tax audit (in years) | 5 years

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_IncomeTaxContingencyLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of taxable years open for state tax audit + References No definition available. + Details
Name: | wfx_NumberOfTaxableYearsOpenForTaxAudit
Namespace Prefix: | wfx_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |