Note 11 - Employee Benefit Plans (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
401(k) Retirement Plan [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 1.2	$ 0.8	$ 0.6
Defined Contribution Retirement Plan for Proto Labs Limited Employees [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.2
Minimum Number Of Employee Working Hours Required To Be Eligible To Participate In 401K Plan	20
Minimum Service Period Of Employees To Avail Benefit Under Defined Contribution Benefit Plan	90 days
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	50.00%