Accumulated Other Comprehensive Loss - Schedule of Changes in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	$ 840,183	$ 646,340	$ 675,366	$ 562,491
Other comprehensive income (loss) before reclassifications	4,147	(6,792)	(15,480)	(3,773)
Amounts reclassified from accumulated other comprehensive loss	815	181	513	951
Total other comprehensive income (loss), net of tax	4,962	(6,611)	(14,967)	(2,822)
End of period	915,037	675,255	915,037	675,255
Post-retirement plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(9,018)	(20,124)	(9,068)	(20,955)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive loss	17	447	67	1,278
Total other comprehensive income (loss), net of tax	17	447	67	1,278
End of period	(9,001)	(19,677)	(9,001)	(19,677)
Derivatives designated as cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(22,101)		(2,122)
Other comprehensive income (loss) before reclassifications	4,147		(15,480)
Amounts reclassified from accumulated other comprehensive loss	798		446
Total other comprehensive income (loss), net of tax	4,945		(15,034)
End of period	(17,156)		(17,156)
Other comprehensive income (loss) before reclassifications, tax	1,500		5,500
Derivatives designated as cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period		8,807		5,849
Other comprehensive income (loss) before reclassifications		(6,792)		(3,773)
Amounts reclassified from accumulated other comprehensive loss		(266)		(327)
Total other comprehensive income (loss), net of tax		(7,058)		(4,100)
End of period		1,749		1,749
Other comprehensive income (loss) before reclassifications, tax		2,400		1,300
Totals
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(31,119)	(11,317)	(11,190)	(15,106)
End of period	$ (26,157)	$ (17,928)	$ (26,157)	$ (17,928)