Stock-Based Compensation (Details Textual) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
[Line Items]
Shares originally authorized for issuance under 2019 Plan					2,500
Shares available for issuance under 2017 Plan	4,800		4,800
Incremental expense associated with equity modifications	$ 0.2	$ 0.2	$ 0.3	$ 0.4
Stock options [Member]
[Line Items]
Weighted-average grant-date fair value of stock options granted	$ 0	$ 28.93	$ 0.00	$ 28.93
Total intrinsic value of stock options exercised	$ 23.9	$ 3.8	$ 25.8	$ 11.4
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	2.1		$ 2.1
Weighted-average remaining period over which cost is expected to be recognized			1 year 10 months 17 days
Restricted stock awards and units [Member]
[Line Items]
Total fair value of shares vested	15.2	5.7	$ 53.4	37.3
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	119.4		$ 119.4
Weighted-average remaining period over which cost is expected to be recognized			2 years 8 months 1 day
Granted number of units (based on performance at 100% of targeted levels)			958
Performance-based restricted stock units [Member]
[Line Items]
Total fair value of shares vested	0.0	$ 0.0	$ 26.6	$ 8.1
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	38.0		$ 38.0
Weighted-average remaining period over which cost is expected to be recognized			1 year 8 months 1 day
Granted number of units (based on performance at 100% of targeted levels)			310
Employee stock purchase plan [Member]
[Line Items]
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	$ 7.7		$ 7.7
Weighted-average remaining period over which cost is expected to be recognized			1 year 5 months 8 days
Shares issued during period under employee stock purchase plan	135	150	135	150
Weighted-average purchase price of shares issued during period under employee stock purchase plan	$ 56.60	$ 43.04	$ 56.60	$ 43.04
Revenue [Member] \| Performance-based restricted stock units [Member]
[Line Items]
Granted number of units (based on performance at 100% of targeted levels)			155
Award terms			performance conditions based on the compound annual growth rate of revenue over the three-year period ending December 31, 2021, vesting in full in three years with the number of shares ultimately earned ranging from zero to 250% of the target number of shares
Relative TSR [Member] \| Performance-based restricted stock units [Member]
[Line Items]
Granted number of units (based on performance at 100% of targeted levels)		6	155	122
Award terms		market conditions based on the Company's total stockholder return ("TSR") relative to that of the Russell 2000 Index over the three-year period ending December 31, 2020, vesting in full in three years with the number of shares ultimately earned ranging from zero to 200% of the target number of shares	market conditions based on the Company's TSR relative to that of the Russell 2000 Index over the three-year period ending December 31, 2021, vesting in full in three years with the number of shares ultimately earned ranging from zero to 200% of the target number of shares
Net income growth [Member] \| Performance-based restricted stock units [Member]
[Line Items]
Granted number of units (based on performance at 100% of targeted levels)		5	0	122
Award terms		performance conditions based on the compound annual growth rate of net income over the three-year period ending December 31, 2020, vesting in full in three years with the number of shares ultimately earned ranging from zero to 200% of the target number of shares
Other individual and team goals [Member] \| Performance-based restricted stock units [Member]
[Line Items]
Granted number of units (based on performance at 100% of targeted levels)			0

Medidata Solutions, Inc. 10-Q