Unaudited Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Comprehensive income (loss)
Net income (loss)	$ 37,990	$ 36,913	$ (33,511)	$ (19,035)
Other comprehensive income (loss):
Foreign currency translation adjustment	2,233	(2,045)	4,591	(5,149)
(Loss) income on cash flow hedges	(137)	361	(303)	1,356
Less tax effect of other comprehensive (loss) income items	(508)	1,455	(1,050)	935
Other comprehensive income (loss)	1,588	(229)	3,238	(2,858)
Comprehensive income (loss)	39,578	36,684	(30,273)	(21,893)
Less comprehensive income (loss) attributable to Summit Holdings	1,576	1,353	(1,087)	(932)
Comprehensive income (loss) attributable to Summit Inc.	38,002	35,331	(29,186)	(20,961)
Summit Materials, LLC
Comprehensive income (loss)
Net income (loss)	53,501	46,602	(38,063)	(21,994)
Other comprehensive income (loss):
Foreign currency translation adjustment	2,233	(2,045)	4,591	(5,149)
(Loss) income on cash flow hedges	(137)	361	(303)	1,356
Other comprehensive income (loss)	2,096	(1,684)	4,288	(3,793)
Comprehensive income (loss) attributable to Summit Inc.	$ 55,597	$ 44,918	$ (33,775)	$ (25,787)