Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jul. 01, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accrued Liabilities, Current	$ 126,774	$ 126,500
Liabilities, Current	175,626	176,329
Deferred income taxes	8,364	7,577
Retained earnings	231,147	209,381
Stockholders' Equity Attributable to Parent	475,687	457,106
Revenues	246,403		$ 206,816
Cost of Revenue	194,927		164,850
Gross Profit	51,476		41,966
Selling, General and Administrative Expense	29,213		26,305
Operating Income (Loss)	22,263		15,661
Income before income taxes	24,136		15,651
Income Tax Expense (Benefit)	4,445		3,898
Net income	19,691		11,753
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accrued Liabilities, Current	128,418
Liabilities, Current	177,270
Deferred income taxes	7,923
Retained earnings	229,944
Stockholders' Equity Attributable to Parent	474,484
Revenues	232,734
Cost of Revenue	182,538
Gross Profit	50,196
Selling, General and Administrative Expense	28,905
Operating Income (Loss)	21,291
Income before income taxes	23,164
Income Tax Expense (Benefit)	4,220
Net income	18,944
Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	(1,280)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	(747)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	6,500		$ 5,100
Revenue from Contract with Customer [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	(13,669)
Cost of Sales [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	(12,389)
Selling, General and Administrative Expenses [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	(308)
Operating Income (Loss) [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	(972)
Other Expense [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	225
Accrued Liabilities [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	1,644	$ 600
Other Current Liabilities [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	1,644
Deferred Tax Asset [Domain]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	(441)
Retained earnings
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	(1,203)
Stockholders' Equity, Total [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	$ (1,203)