Acquisition of Mophie Inc. - Assets Acquired and Liabilities Assumed (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Mar. 03, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 12,272,000	$ 12,272,000		$ 0
Mophie Inc
Business Acquisition [Line Items]
Cash and cash equivalents			$ 1,779,000
Trade receivables (gross contractual receivables of $12,914)			12,823,000
Inventories			24,911,000
Inventories			22,325,000
Inventory step-up			2,586,000
Prepaid expenses and other assets			1,073,000
Prepaid expenses			700,000
Other assets			373,000
Income tax receivable			11,814,000
Deferred tax assets			16,168,000
Property and equipment			10,191,000
Land held for sale			325,000
Amortizable identifiable intangible assets			43,812,000
Goodwill			12,272,000
Accounts payable			(37,359,000)
Income tax payable			(196,000)
Accrued liabilities			(5,163,000)
Deferred revenue			(9,000)
Sales returns liability			(29,584,000)
Deferred tax liabilities			0
Other noncurrent liabilities			(513,000)
Total			62,344,000
Business Acquisitions [Parenthetical] [Abstract]
Gross contractual receivables			12,914,000
Prelminary Allocation | Mophie Inc
Business Acquisition [Line Items]
Cash and cash equivalents			1,779,000
Trade receivables (gross contractual receivables of $12,914)			13,483,000
Inventories			32,335,000
Inventory step-up			6,937,000
Prepaid expenses			485,000
Other assets			200,000
Income tax receivable			10,958,000
Deferred tax assets			24,925,000
Property and equipment			10,191,000
Land held for sale			325,000
Amortizable identifiable intangible assets			45,463,000
Goodwill			14,092,000
Accounts payable			(34,228,000)
Income tax payable			(196,000)
Accrued liabilities			(5,185,000)
Deferred revenue			(800,000)
Sales returns liability			(14,468,000)
Deferred tax liabilities			(17,978,000)
Other noncurrent liabilities			(513,000)
Total			87,805,000
Adjustments to Working Capital and Fair Value | Mophie Inc
Business Acquisition [Line Items]
Cash and cash equivalents			0
Trade receivables (gross contractual receivables of $12,914)			(660,000)
Inventories			(10,010,000)
Inventory step-up			(4,351,000)
Prepaid expenses			215,000
Other assets			173,000
Income tax receivable			856,000
Deferred tax assets			(8,757,000)
Property and equipment			0
Land held for sale			0
Amortizable identifiable intangible assets			(1,651,000)
Goodwill			(1,820,000)
Accounts payable			(3,131,000)
Income tax payable			0
Accrued liabilities			22,000
Deferred revenue			791,000
Sales returns liability			(15,116,000)
Deferred tax liabilities			17,978,000
Other noncurrent liabilities			0
Total			$ (25,461,000)