Income Taxes - Reconciliation Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance at beginning of period	$ 16,531	$ 15,412	$ 13,062
Additions from G&K acquisition	2,084
Additions for tax positions of prior years	2,520	3,259	4,001
Statute expirations	(2,734)	(2,092)	(1,603)
Settlements	(1,044)	(48)	(48)
Balance at end of period	$ 17,357	$ 16,531	$ 15,412