Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, with jurisdictional netting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32537-109319

Summary of Significant Accounting Policies - Goodwill, Income Taxes and VIE (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Jul. 20, 2017 USD ($)	Jul. 27, 2016
Goodwill
Goodwill impairment	$ 0	$ 0
Income Taxes
Unrecognized tax benefits	7,300	0
Deferred tax asset	125,760	$ 193,859
Variable Interest Entity
Ownership interest (as a percent)				29.40%
Carrying amount asset	18,799
Maximum exposure to loss	18,799
VIE's assets	$ 41,936
Share-Based Compensation
Number of days prior to the grant that common stock and restricted stock units fair value is determined based on	3 days
JV building microwave communication networks in US and Asia
Variable Interest Entity
Number of other investors in JV \| item	9
Ownership of voting shares of JV held be each investor (as a percent)	11.00%
Ownership of equity of JV held be each investor (as a percent)	11.00%
JV building microwave communication networks in US and Europe
Variable Interest Entity
Ownership of voting shares (as a percent)	50.00%
Ownership interest (as a percent)	50.00%
KCG
Income Taxes
Deferred tax asset	$ 43,500		$ 23,900