Commitments and Contingencies - Contingent Payments (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 03, 2016
Business Acquisition, Contingent Consideration [Line Items]
(Gain) loss on disputed mophie purchase price	$ 6,967	$ 6,967	$ (24,317)	$ 0
Mophie Inc
Business Acquisition, Contingent Consideration [Line Items]
Contingent payments	14,967				$ 12,139
Cash collected from duty recoveries	2,828
Settlement amount	8,000
(Gain) loss on disputed mophie purchase price	$ 6,967