Leases - ROU assets and liabilities (Details) - USD ($) $ in Thousands	Jun. 27, 2020	Mar. 28, 2020
ROU assets and liabilities
Finance lease assets	$ 10,217	$ 10,444
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Total lease assets	Total lease assets
Operating lease assets	$ 154,481	$ 159,799
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Total lease assets	Total lease assets
Total lease assets	$ 164,698	$ 170,243
Current finance lease liabilities	$ 1,029	$ 1,019
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Total short-term lease liabilities	Total short-term lease liabilities
Current operating lease liabilities	$ 33,926	$ 33,760
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Total short-term lease liabilities	Total short-term lease liabilities
Total short-term lease liabilities	$ 34,955	$ 34,779
Finance Lease, Liability, Noncurrent	$ 12,795	$ 12,954
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Total long-term lease liabilities	Total long-term lease liabilities
Operating Lease, Liability, Noncurrent	$ 142,848	$ 147,981
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Total long-term lease liabilities	Total long-term lease liabilities
Total long-term lease liabilities	$ 155,643	$ 160,935
Total lease liabilities	$ 190,598	$ 195,714