Summary of Significant Accounting Policies - Variable Interest Entities (Details) $ in Thousands	1 Months Ended
Oct. 31, 2016 party	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Variable Interest Entity [Line Items]
Equity investment, Carrying Amount, Asset		$ 18,254	$ 18,799
Equity investment, Carrying Amount, Liability		0	0
Equity investment, Maximum Exposure to Loss		18,254	18,799
Equity investment, VIEs' assets		$ 49,450	$ 41,936
JV building microwave communication networks in US and Asia
Variable Interest Entity [Line Items]
Number of other investors in JV \| party	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 [Line Items]
Ownership of voting shares (as a percent)		50.00%
Ownership interest (as a percent)		50.00%

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The amount of assets reported by an equity method investment of the entity.

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Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

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Carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

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Percentage of voting equity interests acquired in a joint venture.

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The number of other investors in a joint venture.

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The percentage ownership of equity of joint venture held be each investor.

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The percentage ownership of voting shares of joint venture held be each investor.

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