Note 6 - Reconciliation of Common Shareholders' Equity, Common Shares and Earnings Per Share (Details Textual) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	May 11, 2015
Maximum per Share Differences Between Basic and Diluted Earnings per Share in Total or from Continuing or Discontinued Operations	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Distribution Agreement [Member]
Agreement to Sell Shares, Value					$ 75