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 12 Months Ended
Jul. 27, 2017
Jul. 27, 2016
Mar. 31, 2017
Aug. 31, 2016
Aug. 31, 2015
Mar. 31, 2017
Mar. 31, 2016
Dec. 31, 2014
Jan. 18, 2018
Dec. 21, 2017
Dec. 31, 2016
Jan. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                        
Stock repurchase program, authorized amount             $ 50,000,000.0          
Stock repurchase program, remaining authorized amount                     $ 44,800,000  
Income recorded as a result of remeasurement           $ 2,920,000 5,865,000          
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           $ (400,000) $ 5,900,000          
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            
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]                        
Number of 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 | Equity Incentive Plan, 2017                        
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 $ 8.40                      
Common stock warrants | Row 44 Warrants                        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                        
Warrants outstanding                       21,062,500
Options outstanding                       721,897
Number of warrants, as converted (in shares)     689,481     689,481            
Public Warrants | Quotes prices in active markets (Level 1) | 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            
Sponsor Warrants | Public SPAC Warrants                        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                        
Exercise price per warrant (in usd per share)     $ 11.50     $ 11.50            
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                
Share price of common stock (in usd per share)     $ 12.00 $ 12   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                
Share price of common stock (in usd per share)     $ 10.00 $ 10   $ 10.00         $ 10