Fair Value Measurements and Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair value, assets measured on recurring basis [Table Text Block]

Our assets and liabilities measured at fair value on a recurring basis at December 31, 2018 and December 31, 2017, were as follows:

			Fair Value Measurements at December 31, 2018 Using:
	Total Carrying Value at		Quoted prices in active markets		Significant other observable inputs		Significant unobservable inputs
Description	December 31, 2018		(Level 1)		(Level 2)		(Level 3)
Assets:
Assets invested for self-insurance, classified as other assets, noncurrent	$	15,379	$	15,379	$	—	$	—
Defined benefit pension plan assets	3,758		—		3,758		—
Liabilities:
Deferred compensation	$	2,459	$	—	$	2,459	$	—

U. Fair Value Measurements and Financial Instruments (continued)

			Fair Value Measurements at December 31, 2017 Using:
	Total Carrying Value at		Quoted prices in active markets		Significant other observable inputs		Significant unobservable inputs
Description	December 31, 2017		(Level 1)		(Level 2)		(Level 3)
Assets:
Assets invested for self-insurance, classified as other assets, noncurrent	$	19,422	$	19,422	$	—	$	—
Defined benefit pension plan assets	7,105		6,208		897		—
Liabilities:
Deferred compensation	$	2,146	$	—	$	2,146	$	—

Fair value, by balance sheet grouping [Table Text Block]

Financial instruments classified as noncurrent liabilities and their carrying values and fair values were as follows:

	December 31, 2018				December 31, 2017
	Carrying Value		Fair Value		Carrying Value		Fair Value
Revolving credit facility, noncurrent	$	93,500	$	93,500	$	100,000	$	100,000
Senior unsecured notes	56,000		56,002		12,000		12,389
Term loans, noncurrent	6,662		6,868		7,935		10,038
Total	$	156,162	$	156,370	$	119,935	$	122,427