Dividends (Details Textual) - USD ($) $ / shares in Units, $ in Millions								1 Months Ended					3 Months Ended		6 Months Ended
	Jun. 09, 2017	May 03, 2017	Apr. 14, 2017	Mar. 03, 2017	Jul. 08, 2016	Jun. 01, 2016	Mar. 02, 2016	Dec. 23, 2016	Nov. 21, 2016	Sep. 30, 2016	Aug. 30, 2016	Apr. 15, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Common Stock, Dividends, Per Share, Declared													$ 0.30	$ 0.25	$ 0.60	$ 0.50
Dividends	$ 1.8		$ 1.8		$ 1.5			$ 2.9		$ 1.8		$ 1.5
Common Class [Member]
Common Stock, Dividends, Per Share, Declared		$ 0.30		$ 0.30		$ 0.25	$ 0.25		$ 0.30		$ 0.30
Common Class B [Member]
Common Stock, Dividends, Per Share, Declared									$ 0.20