Segment Information - Reportable Segments Adjusted Working Capital and Assets (Details) - USD ($)	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
Segment Reporting Information [Line Items]
Document Fiscal Year Focus									2018
Revenues	$ 223,800,000	$ 236,200,000	$ 188,400,000	$ 178,500,000	$ 215,500,000	$ 196,000,000.0	$ 164,400,000	$ 168,300,000	$ 826,900,000	$ 744,200,000	$ 755,700,000
Total assets	1,547,900,000				1,549,800,000				1,547,900,000	1,549,800,000
Disposal Group, Including Discontinued Operation, Assets	0				1,700,000				0	1,700,000
Operating segments | Audio
Segment Reporting Information [Line Items]
Revenues									682,200,000	637,400,000	661,900,000
Total assets	1,409,100,000				1,430,900,000				1,409,100,000	1,430,900,000
Operating segments | Precision Devices
Segment Reporting Information [Line Items]
Revenues									144,700,000	106,800,000	$ 93,800,000
Total assets	136,900,000				103,400,000				136,900,000	103,400,000
Intra-segment eliminations
Segment Reporting Information [Line Items]
Total assets	$ 1,900,000				$ 13,800,000				$ 1,900,000	$ 13,800,000