Segment and Geographical Information - Reconciliation of Segment Gross Profit to Condensed Consolidated GAAP Gross Profit) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Segment Reporting Information [Line Items]
Gross profit	$ 37,140	$ 45,495	$ 91,976	$ 77,403
Construction revenue on solar services contracts	274,806	286,042	783,019	690,608
Gain on sale and impairment of residential lease assets			815	36,709
Stock-based compensation			18,788	18,927
Operating Segments
Segment Reporting Information [Line Items]
Gross profit	36,731	47,541	90,128	78,210
Construction revenue on solar services contracts	282,100	317,379	821,020	841,495
Intersegment Eliminations
Segment Reporting Information [Line Items]
Gross profit	1,752	939	11,604	19,004
Construction revenue on solar services contracts	(7,294)	(15,612)	(32,816)	(26,237)
Gross Profit \| Segment Reconciling Items
Segment Reporting Information [Line Items]
Legacy utility and power plant projects	0	7	34	(993)
Legacy sale-leaseback transactions	0	181	(20)	4,688
Construction revenue on solar services contracts	0	(1,160)	(4,735)	(18,052)
Gain on sale and impairment of residential lease assets	469	511	1,375	1,268
Stock-based compensation	(623)	(741)	(1,653)	(1,370)
Amortization of intangible assets	$ (1,189)	$ (1,783)	$ (4,757)	$ (5,352)

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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.

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Amount of noncash expense for share-based payment arrangement.

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