Notes Payable, Long-Term Debt and Capital Lease Obligations (Details 4) $ in Millions	May. 31, 2015 USD ($)
7.750% Senior Notes Due 2016
Debt Instrument [Line Items]
Estimated fair value of senior notes	$ 332.5
8.250% Senior Notes Due 2018
Debt Instrument [Line Items]
Estimated fair value of senior notes	460.0
5.625% Senior Notes Due 2020
Debt Instrument [Line Items]
Estimated fair value of senior notes	436.9
4.700% Senior Notes due 2022
Debt Instrument [Line Items]
Estimated fair value of senior notes	$ 522.5