Dividends (Details Textual) - USD ($) $ / shares in Units, $ in Thousands								1 Months Ended			3 Months Ended
	Dec. 07, 2017	Oct. 13, 2017	Sep. 13, 2017	Jun. 09, 2017	May 03, 2017	Apr. 14, 2017	Mar. 03, 2017	Mar. 30, 2018	Feb. 28, 2018	Jan. 05, 2018	Mar. 31, 2018	Mar. 31, 2017
Common Stock, Dividends, Per Share, Declared			$ 0.30				$ 0.30				$ 0.3	$ 0.3
Dividends Payable, Date to be Paid									Mar. 30, 2018
Dividends Payable, Date of Record								Mar. 12, 2018
Dividends		$ 1,800				$ 1,800				$ 6,500
Dividends Payable								$ 1,800
Payments of Ordinary Dividends, Common Stock				$ 1,800							$ 8,311	$ 0
Dividends Payable, Date Declared									Feb. 28, 2018
Common Class A [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.30				$ 0.30				$ 0.30
Common Class B [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.80								$ 0.30