Quarterly report pursuant to Section 13 or 15(d)

Common Stock, Share-based Awards and Warrants - Narrative (Details)

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Common Stock, Share-based Awards and Warrants - Narrative (Details) - USD ($)
 1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
Jul. 27, 2017
Jul. 27, 2016
Mar. 31, 2017
Aug. 31, 2016
Aug. 31, 2015
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2014
Jan. 18, 2018
Dec. 21, 2017
Dec. 31, 2016
Mar. 31, 2016
Jan. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Stock repurchase program, authorized amount                           $ 50,000,000  
Stock repurchase program, remaining authorized amount           $ 44,800,000   $ 44,800,000              
Income recorded as a result of remeasurement           $ (445,000) $ 10,926,000 2,475,000 $ 16,791,000            
Number of warrants authorized for repurchase                   $ 25,000,000.0          
Number of additional warrants authorized for repurchase         $ 20,000,000.0                    
Amount of available for warrants               $ 16,700,000              
Equity Incentive Plan, 2013                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Number of shares authorized (in shares)                         11,000,000    
Public SPAC Warrants                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Warrants outstanding           6,173,000   6,173,000              
Income recorded as a result of remeasurement           $ 200,000 $ 10,900,000 $ (200,000) $ 16,800,000            
Term of warrants               5 years              
Closing stock price for 20 or 30 days to trigger call of warrants (usd per share)               $ 17.50              
Class of warrant or right, threshold days               20 days              
Number of consecutive days               30 days              
Redemption by issuer, price (usd per share)           $ 0.01   $ 0.01              
Estimated proceeds if warrants called               $ 71,000,000              
Emerging Markets Communications LLC                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Deferred compensation to be paid   $ 25,000,000                          
Common Stock | UMG Recordings                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Stock issued during period, litigation (in shares)       1,800,000                      
Common Stock | Emerging Markets Communications LLC                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Stock issued during period, acquisitions (in shares)   5,500,000                          
Subsequent Event | Equity Incentive Plan, 2013                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Shares issuable                     7,070,298        
Subsequent Event | Equity Incentive Plan, 2013 | Employee Stock Options                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Shares available for grant                       2,097,846      
Subsequent Event | Twenty Seventeen Equity Incentive Plan                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Number of shares authorized (in shares)                       6,500,000      
Subsequent Event | Common Stock | Emerging Markets Communications LLC                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Stock issued during period, acquisitions (in shares) 5,000,000                            
Price per share of stock issued during period, acquisitions (in usd per share) $ 8.40                            
Price Per Share Scenario Two | Common Stock | UMG Recordings                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Stock issued during period, litigation (in shares)     400,000 400,000.0                      
Share price of common stock (in usd per share)     $ 12.00 $ 12   12.00   $ 12.00         $ 12.00    
Price Per Share Scenario One | Common Stock | UMG Recordings                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Stock issued during period, litigation (in shares)     500,000 500,000.0                      
Share price of common stock (in usd per share)     $ 10.00 $ 10   10.00   10.00         $ 10.00    
Common stock warrants | Row 44 Warrants                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Warrants outstanding                             21,062,500
Number of shares outstanding                             721,897
Sponsor Warrants | Public SPAC Warrants                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Warrant exercise price (in usd per share)           $ 11.50   $ 11.50              
Quotes prices in active markets (Level 1) | Public Warrants | Public SPAC Warrants                              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Number of warrants (in shares)           6,173,228   6,173,228