Supplemental Financial Information - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Supplemental Income Statement Elements [Abstract]
Interest on revolving credit facility	$ 1,388	$ 2,179	$ 2,467	$ 4,430
Interest rate swap settlements	336	(79)	422	(201)
Line of credit fees	152	127	318	253
Debt issuance amortization costs	138	138	276	276
Interest on finance leases	32	31	65	63
Interest income	(269)	(375)	(589)	(864)
Other	2	17	27	19
Total interest expense, net	$ 1,779	$ 2,038	$ 2,986	$ 3,976