Revenues (Summary of Contract Balances) (Details) - USD ($) $ in Thousands	Sep. 29, 2018	Apr. 01, 2018	Mar. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net of allowance for doubtful accounts of $2,454 and $2,982	$ 104,009		$ 99,150
Costs/estimated earnings in excess of billings on uncompleted contracts	50,826		52,696
Billings in excess of costs/estimated earnings on uncompleted contracts	12,176		12,547
Deferred revenue	23,904		27,420
Deferred revenue - long-term	3,503
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net of allowance for doubtful accounts of $2,454 and $2,982	103,993		99,150
Costs/estimated earnings in excess of billings on uncompleted contracts	51,963		52,696
Billings in excess of costs/estimated earnings on uncompleted contracts	12,598		12,547
Deferred revenue	24,484		27,420
Deferred revenue - long-term			$ 2,758
Difference between Revenue Guidance in Effect before and after Topic 606 \| Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net of allowance for doubtful accounts of $2,454 and $2,982	(16)
Accounts receivable, net of allowance for doubtful accounts		$ 4,859
Accounts receivable, net of allowance for doubtful accounts, % Change		5.00%
Costs/estimated earnings in excess of billings on uncompleted contracts	1,137	$ (1,371)
Costs/estimated earnings in excess of billings on uncompleted contracts		$ (1,870)
Costs/estimated earnings in excess of billings on uncompleted contracts, % Change		(4.00%)
Billings in excess of costs/estimated earnings on uncompleted contracts	422	$ 455
Billings in excess of costs/estimated earnings on uncompleted contracts		$ (371)
Billings in excess of costs/estimated earnings on uncompleted contracts, % Change		(3.00%)
Deferred revenue	$ 580
Deferred revenue - current		$ (3,516)
Deferred revenue - current, % Change		(13.00%)
Deferred revenue - long-term		$ 745
Deferred revenue - long-term, % Change		27.00%

BLACK BOX CORP 10-Q