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Stockholders’ Equity and Stock Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands |  |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 07, 2021 | Aug. 23, 2021 | Feb. 01, 2021 | Dec. 31, 2020 | Feb. 28, 2020 | Sep. 15, 2014 | May 31, 2021 | Dec. 31, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020 | Sep. 29, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsidiary equity units for which investor has right to convert to common stock |  |  |  |  |  |  |  |  | 500,000 |  | 500,000 |  |  |
Stock Repurchase Program, Authorized Amount |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 50,000
2014 Stock Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock authorized and reserved for issuance |  |  |  |  |  |  |  |  | 5,027,201 |  | 5,027,201 |  |  |
Shares available |  |  |  |  |  |  |  |  | 1,205,398 |  | 1,205,398 |  |  |
Percentage of increase in number of shares of common stock issued and outstanding |  |  |  | 5.00% |  |  |  |  |  |  | 5.00% |  |  |
Additional common stock authorized and reserved for future issuance |  |  |  | 879,216 |  |  |  |  |  |  |  |  |  |
Common Class B Units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Conversion ratio |  |  |  |  |  |  |  |  |  |  | one |  |  |
Common Class A [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of units owned |  |  |  |  |  |  |  |  | 100.00% |  | 100.00% |  |  |
PDV Spectrum Holding Company, LLC [Member] | Common Class B Units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock issued during period value to purchase of assets |  |  |  |  |  | $ 10,000 |  |  |  |  |  |  |  |
Proceeds from investment, shares |  |  |  |  |  | 500,000 |  |  |  |  |  |  |  |
Sale of stock, price per share |  |  |  |  |  | $ 20.00 |  |  |  |  |  |  |  |
Restricted Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock compensation expense |  |  |  |  |  |  |  |  | $ 2,400 | $ 4,000 | $ 5,000 | $ 5,700 |  |
Unvested compensation expense |  |  |  |  |  |  |  |  | 24,500 |  | $ 24,500 |  |  |
Weighted average period of recognition of unrecognized compensation cost |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |
Awards issued |  |  |  |  |  |  |  |  |  |  | 348,683 |  |  |
Restricted Stock [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock compensation expense |  |  |  |  |  |  |  |  | 2,000 | 3,700 | $ 4,300 | 5,300 |  |
Restricted Stock [Member] | Research and Development Expense [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock compensation expense |  |  |  |  |  |  |  |  | 200 | 200 | 400 | 300 |  |
Restricted Stock [Member] | Sales And Support [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock compensation expense |  |  |  |  |  |  |  |  | 200 | $ 62 | 300 | $ 100 |  |
Restricted Stock [Member] | Chief Executive Officer [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Awards issued |  | 50,000 |  |  |  |  |  |  |  |  |  |  |  |
Performance-Based Restricted Stock Units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage share payout |  |  |  |  | 50.00% |  |  |  |  |  |  |  | 50.00% |
Awards issued |  |  |  |  | 95,538 |  |  |  |  | 91,216 |  |  |  |
Performance-Based Restricted Stock Units [Member] | Lease Agreements, 900 MHz [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Awards issued |  |  |  |  | 43,446 |  |  |  |  |  |  |  |  |
Performance-Based Restricted Stock Units [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock compensation expense |  |  |  |  |  |  |  |  |  | $ 4,300 |  |  |  |
Performance-Based Restricted Stock Units [Member] | Chief Executive Officer [Member] | CSPM [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unvested compensation expense |  |  |  |  |  |  |  |  | 1,000 |  | $ 1,000 |  |  |
Weighted average period of recognition of unrecognized compensation cost |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |
Performance Metric |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |
Performance-Based Restricted Stock Units [Member] | Chief Executive Officer [Member] | Selling, General and Administrative Expenses [Member] | CSPM [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock compensation expense |  |  |  |  |  |  |  |  | 100 |  | $ 200 |  |  |
Performance-Based Restricted Stock Units [Member] | Stretch Goal [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage share payout |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |
Performance-Based Restricted Stock Units [Member] | First Anniversary [Member] | Lease Agreements, 900 MHz [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of vesting for stock granted to employees |  |  |  |  | 100.00% |  |  |  |  |  |  |  |  |
Performance-Based Restricted Stock Units [Member] | First Anniversary [Member] | Chief Executive Officer [Member] | CSPM [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting if target metric achieved |  |  |  |  |  |  |  | 15,025 |  |  |  |  |  |
Performance-Based Restricted Stock Units [Member] | Second Anniversary [Member] | Chief Executive Officer [Member] | CSPM [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting if target metric achieved |  |  |  |  |  |  |  | 30,049 |  |  |  |  |  |
Performance-Based Restricted Stock Units [Member] | Third Anniversary [Member] | Chief Executive Officer [Member] | CSPM [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting if target metric achieved |  |  |  |  |  |  |  | 60,098 |  |  |  |  |  |
Stock Options [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock compensation expense |  |  |  |  |  |  |  |  | 500 |  | 900 |  |  |
Unvested compensation expense |  |  |  |  |  |  |  |  | 5,800 |  | $ 5,800 |  |  |
Weighted average period of recognition of unrecognized compensation cost |  |  |  |  |  |  |  |  |  |  | 1 year 10 months 24 days |  |  |
Stock options forfeited |  |  |  |  |  |  | 20,132 |  |  |  |  |  |  |
Adjustments to Additional Paid in Capital, Other |  |  |  |  |  |  | $ (1,000) |  |  |  |  |  |  |
Stock options awarded |  |  |  |  |  |  |  |  |  | 300,000 | 165,768 | 500,000 |  |
Stock Options [Member] | Chief Executive Officer [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock options awarded |  | 100,000 |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award, Expected Life |  | 6 years 7 days |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price |  | $ 57.00 |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate |  | 0.92% |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate |  | 53.18% |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate |  | 0.00% |  |  |  |  |  |  |  |  |  |  |  |
Share based compensation arrangement by share based payment award, fair value assumptions, expected forfeiture rate |  | 0.00% |  |  |  |  |  |  |  |  |  |  |  |
Stock Options [Member] | Executive Chairman [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock options awarded | 65,768 |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award, Expected Life | 5 years 11 months 1 day |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price | $ 60.92 |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate | 0.96% |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate | 53.45% |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate | 0.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Share based compensation arrangement by share based payment award, fair value assumptions, expected forfeiture rate | 0.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Performance-Based Stock Options [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock options awarded |  |  |  |  |  |  |  |  |  |  | 0 |  |  |
TSR Performance Units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock compensation expense |  |  |  |  |  |  |  |  | 200 |  | $ 400 |  |  |
Unvested compensation expense |  |  |  |  |  |  |  |  | $ 2,600 |  | $ 2,600 |  |  |
Weighted average period of recognition of unrecognized compensation cost |  |  |  |  |  |  |  |  |  |  | 3 years 5 months 1 day |  |  |
Awards issued |  |  | 45,000 |  |  |  |  |  |  |  |  |  |  |
TSR Performance Units [Member] | Continued Service And Stock Price Levels [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of vesting for stock granted to employees |  |  |  |  |  |  |  |  |  |  | 25.00% |  |  |
TSR Performance Units [Member] | Continued Service And Stock Price Levels [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of vesting for stock granted to employees |  |  |  |  |  |  |  |  |  |  | 350.00% |  |  |

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- Definition The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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