Pension and Other Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Business Combinations and Acquisitions, Benefit Obligation	$ 72,638,000	$ 168,855,000
Total liabilities	772,493,000	486,542,000
Accrued liabilities	97,397,000	53,210,000
Other non-current liabilities	212,783,000	129,639,000
Charge recorded for contributions to defined contribution plans	3,543,000	3,485,000	$ 2,998,000
Fair value of plan assets at beginning of year	317,868,000
Fair value of plan assets at end of year	321,440,000	317,868,000
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	127,726,000
(Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	17,858,000
Fair value of plan assets at end of year	18,166,000	17,858,000
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Estimated net loss for defined benefit pension plans that will be amortized from accumulated other comprehensive loss	3,227,000
Prior service cost that will be amortized from accumulated other comprehensive loss	6,000
Curtailment charge	247,000
Expected contribution to pension plans in 2015	8,416,000
Employer contribution	$ 6,140,000	$ 5,936,000
Assumed percentage increase for healthcare costs	6.50%
Ultimate healthcare trend rate in five years	5.00%
Discount rate	3.65%	4.03%	3.83%
Net periodic pension cost (benefit)	$ (621,000)	$ (1,208,000)	$ 1,361,000
Fair value of plan assets at beginning of year	317,868,000	204,201,000
Fair value of plan assets at end of year	321,440,000	317,868,000	204,201,000
Pension Plans | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fixed income securities investment return	678,000
Disbursements	370,000
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to pension plans in 2015	$ 519,000
Retirement age	65 years
Percentage of premium contributed	100.00%
Discount rate	3.60%
Net periodic pension cost (benefit)	$ 152,000	278,000	$ 269,000
Postretirement Benefit Plans | American Association of Retired Persons
Defined Benefit Plan Disclosure [Line Items]
Employer contribution	35
Defined Benefit Postretirement Life Insurance
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension cost (benefit)	231,000
Total liabilities	4,508,000
Accrued liabilities	4,368,000
Other non-current liabilities	140,000
Cash Surrender Value of Life Insurance	2,917,000	$ 2,754,000
Magnetek [Member]
Defined Benefit Plan Disclosure [Line Items]
Other non-current liabilities	$ 102,436,000