Other Noncurrent Assets - License Fees (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2011	May 31, 2017	May 31, 2016
Intangible assets
License fees		$ 14.4	$ 15.5
Exclusive distribution rights | Unison Industries
Intangible assets
Term of agreement	10 years
Amount agreed to be paid	$ 20.0
Amount paid	$ 7.0
Amount payable in each calendar year			1.3
Licensing Agreements | Unison Industries
Intangible assets
License fees		$ 7.2	$ 8.8
Amortization period		10 years
Current portion of the deferred payments		$ 1.3
Long-term portion		$ 3.2