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Share-based Compensation - Principal Assumptions Utilized in Valuing SSARs Granted (Details) - Stock Settled Stock Appreciation Rights [Member] - $ / shares
12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period 5 years 5 years 5 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]      
Risk-free interest rate, minimum 1.74% 0.94% 1.53%
Risk-free interest rate, maximum 1.94% 2.14% 1.61%
Expected volatility, minimum 32.42% 35.25% 46.34%
Expected volatility, maximum 32.84% 40.22%  
Weighted average grant date fair value (in dollars per share) $ 3.36 $ 3.69 $ 3.95