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Stock-Based Compensation (Details 4) - Performance-based restricted stock units [Member] - TSR [Member]
6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Assumptions used to estimate fair value of TSR PBRSUs    
Expected volatility - Medidata 46.00% 52.00%
Expected volatility - Comparison index 41.00% 13.00%
Expected term 2 years 10 months 16 days 10 months 21 days
Risk-free interest rate 0.99% 0.12%
Dividend yield 0.00% 0.00%