Asset Sale (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			6 Months Ended		12 Months Ended
	Jan. 31, 2017	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2017	Apr. 30, 2019	Mar. 31, 2019	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale		$ 0	$ 2,971		$ 0
Cash		55,107	58,185		55,107
Gain within operating income		817		$ 0	817	$ 0	$ 2,200
Transition services agreement receivable		12,016	11,999		12,016
Transition services agreement payables		11,769	11,769		11,769
Subsidiaries
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash									$ 100
Other current liabilities | Indemnification agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset sale related contingent liabilities		6,800			$ 6,800
NeoPhotonics Corporation, LLC | Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent of ownership disposed								100.00%
Consideration received pursuant to asset purchase agreement								$ 2,000
Exit fee settlements								$ 2,000
Low Speed Transceiver Products | Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale									3,100	$ 13,900
Reversal loss on disposition of business			$ 200
Write-off of accumulated other comprehensive loss		$ 200
Reclassification from assets held-for-sale	$ 3,400
Assets sold	12,800
Low Speed Transceiver Products | Disposed of by Sale | APAT OE
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration received pursuant to asset purchase agreement	25,000
Proceeds from post-closing transaction services fees under transition services agreement	1,400
Disposal group consideration adjustment	21,600
Consideration adjustment for potential indemnification claims	10,000
Low Speed Transceiver Products | Disposed of by Sale | Prepaid Expenses
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, other									500
Low Speed Transceiver Products | Disposed of by Sale | Property, plant and equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, other									$ 2,600	800
Assets sold	700
Low Speed Transceiver Products | Disposed of by Sale | Inventories
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, other										$ 13,100
Assets sold	$ 12,100