Note 11 - Income Taxes (Details Textual) - USD ($) $ in Millions		3 Months Ended		9 Months Ended			12 Months Ended
	Jun. 20, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Mar. 31, 2017
Deferred Tax Liabilities, Undistributed Foreign Earnings		$ 111.0		$ 111.0	$ 111.0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent					35.00%
Accrued Estimated Foreign Tax Withholdings		53.9		53.9	$ 53.9
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		111.1		111.1	111.1			$ 109.6
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount		(61.5)
Deferred Tax Assets, Valuation Allowance		$ 48.1		48.1	$ 48.1
Effective Income Tax Rate Reconciliation, Percent		32.90%	41.30%		21.60%	28.10%
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount		$ 0.6		2.3		$ 2.4
Undistributed Earnings of Foreign Subsidiaries							$ 367.0
Investment Tax Credit Carryforward [Member]
Deferred Tax Assets, Investments							$ 0.7
Tax Credit Carryforward Expiration Period							20 years
General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Period							20 years
Minimum [Member] | Investment Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year							2022
Minimum [Member] | General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year							2026
Maximum [Member] | Investment Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year							2024
Maximum [Member] | General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year							2036
Deferred Tax Assets, Tax Credit Carryforwards, General Business							$ 82.5
Domestic Tax Authority [Member]
Operating Loss Carryforwards							$ 299.6
Domestic Tax Authority [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year							2029
Domestic Tax Authority [Member] | Maximum [Member]
Tax Credit Carryforward Expiration Year							2036
State and Local Jurisdiction [Member]
Operating Loss Carryforwards							$ 244.7
State and Local Jurisdiction [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year							2018
State and Local Jurisdiction [Member] | Maximum [Member]
Tax Credit Carryforward Expiration Year							2036
Foreign Tax Authority [Member] | Kenya Revenue Authority [Member]
Income Tax Examination, Penalties Paid	$ 2.6
Investment Deduction Percentage	150.00%
Income Tax Examination, Interest Expense	$ 1.2
ISRAEL
National Corporate Tax Rate					16.00%
KENYA
National Corporate Tax Rate					37.50%
U.S. Foreign Tax Credits [Member]
Deferred Tax Assets, Valuation Allowance		47.0		47.0	$ 47.0
Current Year Projected Activity [Member]
Deferred Tax Assets, Valuation Allowance		$ 1.1		$ 1.1	$ 1.1