Pension and Other Post-retirement Benefit Plans - Benefit Schedules (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Number of Fiscal Years	10 years
Target allocation and weighted-average asset allocations
Target Allocation (as a percent)	100.00%
Plan Assets (as a percent)	100.00%
Estimated future pension benefit payments
2015	$ 1,710
2016	1,516
2017	1,727
2018	1,792
2019	1,760
2021- 2025	10,870
Pension
Other changes in plan assets and benefit obligations recognized in Accumulated other comprehensive income
Current year actuarial (gain) loss	(5,125)	$ 12,397	$ (190)
Amortization of actuarial gain (loss)	(698)	(258)	(286)
Current year prior service cost	342	1,006	285
Amortization of prior service cost	(60)	(17)	(4)
Total recognized in other comprehensive income	(5,541)	13,128	(195)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	(2,356)	16,028	2,683
Estimated future pension benefit payments
2015	1,627
2016	1,438
2017	1,654
2018	1,725
2019	1,699
2021- 2025	10,651
Other Benefits
Other changes in plan assets and benefit obligations recognized in Accumulated other comprehensive income
Current year actuarial (gain) loss	(146)	118	95
Amortization of actuarial gain (loss)	191	187	259
Current year prior service cost	0	0	0
Amortization of prior service cost	0	0	0
Total recognized in other comprehensive income	45	305	354
Total recognized in net periodic benefit cost and other comprehensive income (loss)	(127)	$ 147	$ 118
Estimated future pension benefit payments
2015	83
2016	78
2017	73
2018	67
2019	61
2021- 2025	$ 219
Insurance
Target allocation and weighted-average asset allocations
Target Allocation (as a percent)	10.00%
Plan Assets (as a percent)	6.00%
International equities
Target allocation and weighted-average asset allocations
Target Allocation (as a percent)	15.00%
Plan Assets (as a percent)	15.00%
International bonds
Target allocation and weighted-average asset allocations
Target Allocation (as a percent)	60.00%
Plan Assets (as a percent)	63.00%
Other
Target allocation and weighted-average asset allocations
Target Allocation (as a percent)	15.00%
Plan Assets (as a percent)	16.00%