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Stock-Based Compensation - Weighted-average Black-Scholes assumptions (Details)
9 Months Ended
Nov. 30, 2018
Nov. 30, 2017
Expected life (in years) 8 years  
Risk free interest rate, minimum 2.68% 1.79%
Risk free interest rate, maximum 2.98% 2.01%
Expected volatility, minimum 24.82% 12.65%
Expected volatility, maximum 28.24% 18.06%
Expected dividend yield 0.00% 0.00%
Minimum    
Expected life (in years)   2 years
Maximum    
Expected life (in years)   8 years