Earnings Per Share and Dividends - Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands	May 31, 2018	May 31, 2017
Quarter One
Dividends Payable [Line Items]
Dividend per Share (in dollars per share)	$ 0.08	$ 0.08
Total of Cash Dividends Declared	$ 14,588	$ 15,248
Quarter Two
Dividends Payable [Line Items]
Dividend per Share (in dollars per share)	$ 0.08	$ 0.08
Total of Cash Dividends Declared	$ 14,272	$ 15,051
Quarter Three
Dividends Payable [Line Items]
Dividend per Share (in dollars per share)	$ 0.08	$ 0.08
Total of Cash Dividends Declared	$ 13,991	$ 14,840