Quarterly report pursuant to Section 13 or 15(d)

Defined Benefit Pension and Other Postretirement Benefit Plans (Details)

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Defined Benefit Pension and Other Postretirement Benefit Plans (Details)
$ in Thousands
3 Months Ended 9 Months Ended
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Mar. 31, 2019
USD ($)
Defined Benefit Plan Disclosure          
Defined Benefit Plan, Number of Plans     12    
Pension          
Defined Benefit Plan Disclosure          
Contribution by employer     $ 2,900    
Net periodic benefit (income) costs          
Net service cost $ 1,249 $ 1,233 3,745 $ 3,699  
Interest cost 462 478 1,387 1,434  
Expected return on net assets (468) (531) (1,420) (1,594)  
Amortization:          
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) 113 107 338 322  
Prior service cost 21 23 63 69  
Total net periodic benefit cost (credit) 1,377 1,310 4,113 3,930  
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position (86,635)   (86,635)   $ (84,538)
Pension | Maximum          
Defined Benefit Plan Disclosure          
Estimated employer contribution in current fiscal year 5,100   5,100    
Other Benefits          
Net periodic benefit (income) costs          
Net service cost 0 0 0 0  
Interest cost 2 3 7 9  
Expected return on net assets 0 0 0 0  
Amortization:          
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (37) (39) (111) (116)  
Prior service cost 0 0 0 0  
Total net periodic benefit cost (credit) (35) $ (36) (104) $ (107)  
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position (289)   (289)   (312)
Prepaid Expenses and Other Current Assets [Member] | Pension          
Defined Benefit Plan Disclosure          
Assets for Plan Benefits, Defined Benefit Plan (1,191)   (1,191)   (670)
Prepaid Expenses and Other Current Assets [Member] | Other Benefits          
Defined Benefit Plan Disclosure          
Assets for Plan Benefits, Defined Benefit Plan 0   0   0
Accrued Liabilities [Member] | Pension          
Defined Benefit Plan Disclosure          
Assets for Plan Benefits, Defined Benefit Plan (2,808)   (2,808)   (2,753)
Accrued Liabilities [Member] | Other Benefits          
Defined Benefit Plan Disclosure          
Assets for Plan Benefits, Defined Benefit Plan (50)   (50)   (50)
Other Noncurrent Liabilities [Member] | Pension          
Defined Benefit Plan Disclosure          
Assets for Plan Benefits, Defined Benefit Plan (85,018)   (85,018)   (82,455)
Other Noncurrent Liabilities [Member] | Other Benefits          
Defined Benefit Plan Disclosure          
Assets for Plan Benefits, Defined Benefit Plan $ (239)   $ (239)   $ (262)