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Summary of Significant Accounting Policies - Allowance for Credit Losses (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Allowance for Doubtful Accounts Receivable [Roll Forward] |  |  |
Balance at beginning of year | $ 6,907 | $ 5,898 |
Impact of new accounting standard | 695 |  |
Bad debt expense (benefit) | 5,253 | 2,978 | $ 3,562
Deductions for uncollectible receivables written off, net of recoveries | (2,166) | (3,924) |
Credit allowance of acquired companies on the acquisition date | 335 | 1,955 |
Reclass to other current liabilities | (315) |  |
Balance at end of year | 10,709 | 6,907 | $ 5,898
Service |  |  |
Allowance for Doubtful Accounts Receivable [Roll Forward] |  |  |
Balance at beginning of year | 3,192 |  |
Impact of new accounting standard | 310 |  |
Bad debt expense (benefit) | 2,566 |  |
Deductions for uncollectible receivables written off, net of recoveries | (1,431) |  |
Balance at end of year | 4,637 | 3,192 |
Construction |  |  |
Allowance for Doubtful Accounts Receivable [Roll Forward] |  |  |
Balance at beginning of year | 3,400 |  |
Impact of new accounting standard | 331 |  |
Bad debt expense (benefit) | 2,697 |  |
Deductions for uncollectible receivables written off, net of recoveries | (735) |  |
Credit allowance of acquired companies on the acquisition date | 335 |  |
Balance at end of year | 6,028 | 3,400 |
Other. |  |  |
Allowance for Doubtful Accounts Receivable [Roll Forward] |  |  |
Balance at beginning of year | 315 |  |
Impact of new accounting standard | 54 |  |
Bad debt expense (benefit) | (10) |  |
Reclass to other current liabilities | (315) |  |
Balance at end of year | $ 44 | $ 315 |

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