Quarterly report pursuant to Section 13 or 15(d)

Equity Method Investments Schedule of Summarized Financial Information (Details)

v3.8.0.1
Equity Method Investments Schedule of Summarized Financial Information (Details) - USD ($)
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]      
Current assets $ 37,520   $ 35,859
Non-current assets 21,025   21,009
Current liabilities 17,068   15,151
Non-current liabilities 1,012   1,056
Revenue 36,211,000 $ 34,429,000  
Net income 5,899,000 $ 6,449,000  
Schedule of Equity Method Investments [Line Items]      
Carrying value 138,495,000   137,299,000
Wireless Maritime Services      
Schedule of Equity Method Investments [Line Items]      
Carrying value $ 138,495,000   $ 137,299