Business Segment Information - Summary of Net Sales of Company Recognized at a Point in Time Versus Over Time (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total net sales	$ 715,019	$ 578,021	$ 596,219	$ 530,670	$ 687,275	$ 565,584	$ 558,250	$ 497,969	$ 2,419,929	$ 2,309,078	$ 2,167,423
Chemistry Consumables [Member]
Disaggregation of Revenue [Line Items]
Total net sales									400,287	372,157	345,413
Service [Member]
Disaggregation of Revenue [Line Items]
Total net sales									814,936	756,729	707,127
Net Sales Recognized at a Point in Time: [Member]
Disaggregation of Revenue [Line Items]
Total net sales									1,922,542	1,851,734	1,739,778
Net Sales Recognized at a Point in Time: [Member] \| Instrument Systems [Member]
Disaggregation of Revenue [Line Items]
Total net sales									1,204,706	1,180,192	1,114,883
Net Sales Recognized at a Point in Time: [Member] \| Chemistry Consumables [Member]
Disaggregation of Revenue [Line Items]
Total net sales									400,287	372,157	345,413
Net Sales Recognized at a Point in Time: [Member] \| Service [Member]
Disaggregation of Revenue [Line Items]
Total net sales									317,549	299,385	279,482
Net Sales Recognized Over Time: [Member] \| Service [Member]
Disaggregation of Revenue [Line Items]
Total net sales									$ 497,387	$ 457,344	$ 427,645