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BUSINESS COMBINATIONS (Details) - USD ($) $ / shares in Units, $ in Thousands |  |  |  |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Jul. 02, 2019 | Nov. 09, 2018 | Oct. 01, 2018 | Apr. 30, 2018 | Dec. 27, 2019 | Sep. 27, 2019 | Jun. 28, 2019 | Mar. 29, 2019 | Dec. 28, 2018 | Sep. 28, 2018 | Jun. 29, 2018 | Mar. 30, 2018 | Dec. 27, 2019 | Dec. 28, 2018 | Dec. 29, 2017
BUSINESS COMBINATIONS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Par value (in dollars per share) |  |  |  |  | $ 0.01 |  |  |  | $ 0.01 |  |  |  | $ 0.01 | $ 0.01 |
Cash paid at closing |  |  |  |  |  |  |  |  |  |  |  |  | $ 27,000 |  |
Revenues. |  |  |  |  | $ 129,416 | $ 117,494 | $ 104,396 | $ 91,793 | $ 86,438 | $ 71,386 | $ 59,833 | $ 54,595 | 443,099 | $ 272,252 | $ 273,352
Cash paid |  |  |  |  |  |  |  |  |  |  |  |  | 71,756 | 124,344 | $ 14,603
Onsite Energy Corporation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
BUSINESS COMBINATIONS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate Purchase price | $ 24,905 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues. |  |  |  |  |  |  |  |  |  |  |  |  | 7,700 |  |
Cash paid | 24,411 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lime Energy |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
BUSINESS COMBINATIONS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from equity raise |  | $ 50,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate Purchase price |  | 120,000 | $ 122,439 |  |  |  |  |  |  |  |  |  |  |  |
Cash paid at closing |  | $ 56,400 |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues. |  |  |  |  |  |  |  |  |  |  |  |  | $ 158,700 | $ 181,500 |
Cash paid |  |  | $ 122,439 |  |  |  |  |  |  |  |  |  |  |  |
NAM | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
BUSINESS COMBINATIONS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate Purchase price |  |  |  | $ 4,000 |  |  |  |  |  |  |  |  |  |  |
Willdan Energy Solutions | Onsite Energy Corporation | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
BUSINESS COMBINATIONS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate Purchase price | $ 26,400 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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