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Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 28, 2019	Mar. 30, 2019	Dec. 29, 2018	Jun. 01, 2017
Debt
Total debt	$ 1,872,273		$ 1,828,159
Current portion of long-term debt	7,942		6,354
Long-term debt	1,864,331		1,821,805
Gross amount	1,874,255
Debt discount	1,982
Summit Materials, LLC
Debt
Total debt	1,872,273		1,828,159
Current portion of long-term debt	7,942		6,354
Long-term debt	1,864,331		1,821,805
Gross amount	1,874,255
Debt discount	1,982
Term Loan, due 2024
Debt
Total debt	623,140		629,268
Gross amount	624,300		630,600
Debt discount	1,100		1,300
Term Loan, due 2024 \| Summit Materials, LLC
Debt
Total debt	623,140		629,268
Gross amount	624,300		630,600
Debt discount	1,100		1,300
8 1/2% Senior Notes, due 2022
Debt
Total debt	0		$ 250,000
Debt instrument interest rate (as a percent)			8.50%
8 1/2% Senior Notes, due 2022 \| Summit Materials, LLC
Debt
Total debt	0		$ 250,000
Debt instrument interest rate (as a percent)		8.50%	8.50%
6 1/8% Senior Notes, due 2023
Debt
Total debt	649,133		$ 648,891
Gross amount	650,000		650,000
Debt discount	$ 900		1,100
Debt instrument interest rate (as a percent)	6.125%
6 1/8% Senior Notes, due 2023 \| Summit Materials, LLC
Debt
Total debt	$ 649,133		648,891
Gross amount	650,000		650,000
Debt discount	$ 900		1,100
Debt instrument interest rate (as a percent)	6.125%
5 1/8% Senior Notes, due 2025
Debt
Total debt	$ 300,000		300,000
5 1/8% Senior Notes, due 2025 \| Summit Materials, LLC
Debt
Total debt	$ 300,000		300,000	$ 300,000
Debt instrument interest rate (as a percent)	5.125%			5.125%
Senior Notes \| 6 1⁄2% Senior Notes, due 2027
Debt
Total debt	$ 300,000		0
Debt instrument interest rate (as a percent)	6.50%
Senior Notes \| 6 1⁄2% Senior Notes, due 2027 \| Summit Materials, LLC
Debt
Total debt	$ 300,000		$ 0
Debt instrument interest rate (as a percent)	6.50%