Pension and Other Postretirement Benefits - Summary (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 117	$ 120	$ 235	$ 240
Interest expense	1,029	1,155	2,059	2,309
Expected return on plan assets	(1,121)	(1,286)	(2,242)	(2,572)
Amortization of prior service cost	10	11	21	21
Settlement loss	548	518	548	518
Actuarial loss	456	422	912	845
Net periodic pension cost	1,039	940	1,533	1,361
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	4	3	7
Interest expense	82	83	164	166
Amortization of prior service cost	(177)	(177)	(354)	(355)
Actuarial loss	109	109	219	219
Net periodic pension cost	$ 16	$ 19	$ 32	$ 37