Description of Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Allowance for doubtful accounts activity

Activity in our allowance for credit losses was comprised of the following for the periods indicated (in thousands):

	Years ended December 31,
	2020		2019		2018
Beginning balance	$	1,132	$	2,034	$	2,492
Additions	2,541		2,871		234
Deductions	(587)		(3,773)		(692)
Ending balance	$	3,086	$	1,132	$	2,034

Property, plant and equipment estimated useful lives

Depreciation of property, plant and equipment is recognized on a straight-line basis over the following estimated useful lives:

Class of assets	Useful life
Buildings and improvements	5 to 40 years
Machinery, equipment, and furniture and fixtures	3 to 10 years
Leasehold improvements	Shorter of asset life or term of lease

Schedule of antidilutive securities excluded from computation of EPS

The following table presents instruments which were not dilutive and were excluded from the computation of diluted EPS in each period, as well as the weighted average dilutive common stock equivalent shares which were included in the computation of diluted EPS (in thousands): 

	December 31,
	2020	2019	2018
Non-dilutive instruments	52	103	82
Dilutive common stock equivalents	284	34	88