Benefit Plans (Fair value of our pension benefits plan assets) (Details) - USD ($)
$ in Thousands
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]      
Other Investments $ 4,345 $ 5,089 $ 5,484
Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Cash and Cash Equivalents, Fair Value Disclosure 319,581 220,633  
Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Cash and Cash Equivalents, Fair Value Disclosure 0 0  
Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Cash and Cash Equivalents, Fair Value Disclosure 0 0  
Other Defined Benefit Pension Plans [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Insurance Contract 4,345 5,089  
Cash and Cash Equivalents, Fair Value Disclosure 302 450  
Other Investments 14,522 14,720  
Equity Securities, FV-NI 47,187 73,532  
Defined Benefit Plan, Plan Assets, Amount 112,203 117,504 $ 119,441
Debt Securities, Trading 45,847 23,713  
Other Defined Benefit Pension Plans [Member] | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Insurance Contract 0 0  
Cash and Cash Equivalents, Fair Value Disclosure 302 450  
Other Investments 0 0  
Defined Benefit Plan, Plan Assets, Amount 302 450  
Other Defined Benefit Pension Plans [Member] | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Insurance Contract 0 0  
Cash and Cash Equivalents, Fair Value Disclosure 0 0  
Other Investments 14,522 14,720  
Defined Benefit Plan, Plan Assets, Amount 14,522 14,720  
Other Defined Benefit Pension Plans [Member] | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Insurance Contract 4,345 5,089  
Cash and Cash Equivalents, Fair Value Disclosure 0 0  
Other Investments 0 0  
Defined Benefit Plan, Plan Assets, Amount $ 4,345 $ 5,089