Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($) |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Mar. 31, 2019 |
Mar. 31, 2018 |
Dec. 31, 2018 |
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| Changes in the Allowance for Doubtful Accounts [Roll Forward] | |||
| Allowance for doubtful accounts, beginning of period | $ 2,765,000 | $ 3,315,000 | $ 3,315,000 |
| Charges to costs and expenses | 77,000 | 64,000 | |
| Account write-offs and other | (29,000) | (86,000) | |
| Allowance for doubtful accounts, end of period | 2,813,000 | $ 3,293,000 | 2,765,000 |
| Accounts receivable, amounts determined to be uncollectible | $ 0 | $ 0 | |
| Minimum | |||
| Changes in the Allowance for Doubtful Accounts [Roll Forward] | |||
| Accounts receivable retainage, percentage | 5.00% | ||
| Maximum | |||
| Changes in the Allowance for Doubtful Accounts [Roll Forward] | |||
| Accounts receivable retainage, percentage | 10.00% | ||
| X | ||||||||||
- Definition Accounts Receivable Retainage No definition available.
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| X | ||||||||||
- Definition Allowance for Doubtful Accounts Receivable, Charge-offs and Other No definition available.
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| X | ||||||||||
- Definition Contracts Receivable Retainage Allowances and Reserves No definition available.
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| X | ||||||||||
- Definition For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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| X | ||||||||||
- Definition Amount of expense related to write-down of receivables to the amount expected to be collected. Includes, but is not limited to, accounts receivable and notes receivable. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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