Segment and Geographical Information - Reconciliation of Other Significant Reconciling Items from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 27, 2020	Dec. 29, 2019	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019	Dec. 29, 2019
Segment Reporting Information [Line Items]
Segment gross profit as reviewed by CODM	$ 37,140		$ 45,495	$ 91,976	$ 77,403
Adjusted EBITDA	146,405		17,354	223,084	136,775
Residential, Light Commercial
Segment Reporting Information [Line Items]
Revenue	197,710		219,880	590,141	606,994
Segment gross profit as reviewed by CODM	34,779		28,609	94,501	64,428
Adjusted EBITDA	15,521		10,508	31,347	14,277
Residential, Light Commercial
Segment Reporting Information [Line Items]
Revenue	74,334		63,524	175,264	155,773
Segment gross profit as reviewed by CODM	5,120		2,072	14,533	8,031
Adjusted EBITDA	1,228		(8,954)	(1,245)	(27,637)
Others
Segment Reporting Information [Line Items]
Revenue	10,056		33,975	55,615	78,728
Segment gross profit as reviewed by CODM	(3,168)		16,860	(18,906)	5,751
Adjusted EBITDA	(3,192)		35,565	(19,279)	29,864
Operating Segments
Segment Reporting Information [Line Items]
Segment gross profit as reviewed by CODM	36,731		47,541	90,128	78,210
Adjusted EBITDA	13,557	$ 37,119		10,823		$ 16,504
Intersegment Eliminations
Segment Reporting Information [Line Items]
Segment gross profit as reviewed by CODM	1,752		939	11,604	19,004
Intersegment Eliminations | Residential, Light Commercial
Segment Reporting Information [Line Items]
Revenue	0		0	0	0
Intersegment Eliminations | Residential, Light Commercial
Segment Reporting Information [Line Items]
Revenue	0		0	0	0
Intersegment Eliminations | Others
Segment Reporting Information [Line Items]
Revenue	7,293		15,612	32,815	26,237
Dev Co | Operating Segments | Residential, Light Commercial
Segment Reporting Information [Line Items]
Revenue	190,480		217,112	571,237	600,263
Dev Co | Operating Segments | Residential, Light Commercial
Segment Reporting Information [Line Items]
Revenue	73,790		63,127	167,543	155,081
Dev Co | Operating Segments | Others
Segment Reporting Information [Line Items]
Revenue	2,688		8,289	2,233	22,899
Power Co | Operating Segments | Residential, Light Commercial
Segment Reporting Information [Line Items]
Revenue	7,230		2,768	18,904	6,731
Power Co | Operating Segments | Residential, Light Commercial
Segment Reporting Information [Line Items]
Revenue	544		397	7,721	692
Power Co | Operating Segments | Others
Segment Reporting Information [Line Items]
Revenue	$ 75		$ 10,074	$ 20,567	$ 29,592