IDEXX Retirement and Incentive Savings Plan (Details) - 401(k) Plan - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement And Incentive Savings Plan [Line Items]
Contribution match, maximum percent of participants' eligible compensation	5.00%	5.00%	5.00%
Employer contributions	$ 23,400,000	$ 21,100,000	$ 19,000,000.0
Discretionary contributions	$ 0	$ 0	$ 0