Long-term debt and revolving lines of credit - Deferred financing costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 28, 2020	Mar. 30, 2019	Mar. 31, 2018
Long-term debt and revolving lines of credit
Amortization expense of deferred financing costs	$ 1,862	$ 2,351	$ 2,664
Amortization expense of deferred financing costs:
Within 1 year	1,862
2 years	1,862
3 years	1,819
4 years	746
Total	6,289
Senior secured term loan facility
Long-term debt and revolving lines of credit
Deferred financing costs		$ 2,384	9,640
Amortization expense of deferred financing costs:
Within 1 year	1,791
2 years	1,791
3 years	1,791
4 years	746
Total	6,119
Revolving credit facility
Long-term debt and revolving lines of credit
Deferred financing costs			$ 57
Amortization expense of deferred financing costs:
Within 1 year	71
2 years	71
3 years	28
Total	$ 170