Quarterly report pursuant to Section 13 or 15(d)

Equity Method Investments Schedule of Summarized Financial Information (Details)

v3.10.0.1
Equity Method Investments Schedule of Summarized Financial Information (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]          
Current assets $ 41,615   $ 41,615   $ 35,859
Non-current assets 24,229   24,229   21,009
Current liabilities 16,228   16,228   15,151
Non-current liabilities 2,769   2,769   1,056
Revenue 35,690,000 $ 36,696,000 100,596,000 $ 104,141,000  
Net income 7,440,000 $ 6,658,000 17,538,000 $ 17,636,000  
Schedule of Equity Method Investments [Line Items]          
Carrying value 135,975,000   135,975,000   137,299,000
Wireless Maritime Services          
Schedule of Equity Method Investments [Line Items]          
Carrying value $ 135,975,000   $ 135,975,000   $ 137,299