Revenue - Net Sales Related to Key Product Lines, Distribution Channels, and Geographic Regions (Details) - Net Sales	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Product Concentration Risk | Protection (screen protection and cases)
Disaggregation of Revenue [Line Items]
Percentage of sales	52.00%	57.00%	48.00%
Product Concentration Risk | Power (power management and power cases)
Disaggregation of Revenue [Line Items]
Percentage of sales	36.00%	32.00%	41.00%
Product Concentration Risk | Audio
Disaggregation of Revenue [Line Items]
Percentage of sales	5.00%	5.00%	5.00%
Product Concentration Risk | Productivity (keyboards and other)
Disaggregation of Revenue [Line Items]
Percentage of sales	7.00%	6.00%	6.00%
Distribution Channel Concentration Risk | Indirect
Disaggregation of Revenue [Line Items]
Percentage of sales	87.00%	88.00%	89.00%
Distribution Channel Concentration Risk | Website
Disaggregation of Revenue [Line Items]
Percentage of sales	8.00%	8.00%	8.00%
Distribution Channel Concentration Risk | Franchisees
Disaggregation of Revenue [Line Items]
Percentage of sales	5.00%	4.00%	3.00%
Geographic Concentration Risk | United States
Disaggregation of Revenue [Line Items]
Percentage of sales	77.00%	84.00%	84.00%
Geographic Concentration Risk | Europe
Disaggregation of Revenue [Line Items]
Percentage of sales	13.00%	9.00%	9.00%
Geographic Concentration Risk | Other
Disaggregation of Revenue [Line Items]
Percentage of sales	10.00%	7.00%	7.00%