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Share-Based Compensation - Schedule of Assumptions for Stock Options Fair Values (Details) - Options to purchase common stock
12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected stock price volatility (percent) 26.00% 25.00% 21.00%
Expected dividend yield (percent) 0.90% 0.80% 0.70%
Risk-free interest rate (percent) 2.80% 1.70% 1.10%
Expected life (in years) 4 years 7 months 6 days 4 years 6 months 4 years