Note 5 - Earnings Per Common Share - Components Used in Computation of Basic and Diluted Earnings Per Common Share (Details) (Parentheticals)	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015
1.625% Convertible Senior Notes due May 2018 [Member]
Debt Instrument, Interest Rate, Stated Percentage	1.625%	1.625%
0.25% Convertible Senior Notes Due June 2019 [Member]
Debt Instrument, Interest Rate, Stated Percentage	0.25%
1.25% Convertible Senior Notes Due August 2032 [Member]
Debt Instrument, Interest Rate, Stated Percentage	1.25%		1.25%