Accumulated Other Comprehensive Loss - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of year	$ 675,366	$ 562,491	$ 584,873
Other comprehensive income (loss) before reclassifications	(36,440)	3,048	3,295
Amounts reclassified from accumulated other comprehensive loss	1,629	868	1,527
Total other comprehensive (loss) income, net of tax	(34,811)	3,916	4,822
Reclassification of AOCI due to the 2017 Tax Act (4)			(2,851)
End of year	856,356	675,366	562,491
Tax expense (benefit)	(14,600)	2,600	2,900
Post-retirement plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of year	(9,068)	(20,955)	(17,077)
Other comprehensive income (loss) before reclassifications	4,860	10,262	(1,698)
Amounts reclassified from accumulated other comprehensive loss	81	1,625	1,527
Total other comprehensive (loss) income, net of tax	4,941	11,887	(171)
Reclassification of AOCI due to the 2017 Tax Act (4)			(3,707)
End of year	(4,127)	(9,068)	(20,955)
Derivatives designated as cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of year	(2,122)
Other comprehensive income (loss) before reclassifications	(41,300)
Amounts reclassified from accumulated other comprehensive loss	1,548
Total other comprehensive (loss) income, net of tax	(39,752)
End of year	(41,874)	(2,122)
Derivatives designated as cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of year	(2,122)	5,849	0
Other comprehensive income (loss) before reclassifications		(7,214)	4,993
Amounts reclassified from accumulated other comprehensive loss		(757)	0
Total other comprehensive (loss) income, net of tax		(7,971)	4,993
Reclassification of AOCI due to the 2017 Tax Act (4)			856
End of year		(2,122)	5,849
Totals
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of year	(11,190)	(15,106)	(17,077)
End of year	$ (46,001)	$ (11,190)	$ (15,106)

Tax Cuts And Jobs Act Of 2017, Reclassification From AOCI To Retained Earnings

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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