Segment and Geographic Information - Income Before Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting, Reconciling Item for Operating Earnings from Segment to Consolidated [Line Items]
Operating earnings of all reportable segments	$ 84,124,000
Net corporate interest expense	(10,774,000)	$ (10,109,000)	$ (9,062,000)
Goodwill and intangible asset impairment charges	(17,484,000)	(1,056,000)	(19,598,000)
Arbitration and claim settlements	12,552,000	0	0
Restructuring and special charges	0	0	(12,084,000)
Loss on disposition of business line	0	(20,270,000)	0
Income before income taxes	23,637,000	44,131,000	42,262,000
Operating segments
Segment Reporting, Reconciling Item for Operating Earnings from Segment to Consolidated [Line Items]
Operating earnings of all reportable segments	84,124,000	97,781,000	109,169,000
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Earnings from Segment to Consolidated [Line Items]
Unallocated corporate and shared costs and credits	(6,515,000)	(9,321,000)	(13,463,000)
Net corporate interest expense	(10,774,000)	(10,109,000)	(9,062,000)
Stock option expense	(1,885,000)	(1,742,000)	(1,718,000)
Amortization of acquisition-related intangible assets	(11,277,000)	(11,152,000)	(10,982,000)
Goodwill and intangible asset impairment charges	(17,484,000)	(1,056,000)	(19,598,000)
Arbitration and claim settlements	(12,552,000)	0	0
Restructuring and special charges	0	0	(12,084,000)
Loss on disposition of business line	$ 0	$ (20,270,000)	$ 0