Pensions and Other Benefits (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	$ 321,440	$ 317,868
(Level 1)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	182,688	178,218
(Level 2)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	120,586	121,792
(Level 3)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	18,166	17,858
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	220,497	212,301
Equity securities | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	149,435	142,947
Equity securities | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	71,062	69,354
Equity securities | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	0	0
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	99,700	104,622
Fixed income | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	32,010	34,326
Fixed income | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	49,524	52,438
Fixed income | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	18,166	17,858
Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	1,243	945
Cash equivalents | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	1,243	945
Cash equivalents | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	0	0
Cash equivalents | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Asset categories:	$ 0	$ 0