Acquisition of Mophie Inc. - Identifiable Intangible Assets (Details) - Mophie Inc $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Intangible asset class	$ 43,812
Tradenames
Business Acquisition [Line Items]
Intangible asset class	$ 18,348
Weighted-average amortization period	10 years
Patents and technology
Business Acquisition [Line Items]
Intangible asset class	$ 15,225
Weighted-average amortization period	7 years 6 months
Customer relationships
Business Acquisition [Line Items]
Intangible asset class	$ 8,200
Weighted-average amortization period	5 years
Non-compete agreements
Business Acquisition [Line Items]
Intangible asset class	$ 1,796
Weighted-average amortization period	5 years
Backlog
Business Acquisition [Line Items]
Intangible asset class	$ 243
Weighted-average amortization period	3 months 18 days