Discontinued Operations - Narrative (Details) $ in Thousands	3 Months Ended
	Aug. 31, 2015 USD ($) transaction buyer	Aug. 31, 2014 USD ($)	May. 31, 2015 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investments	$ 14,600		$ 225,700
Gain on sale of stock of an equity method investment, net of tax		$ 13,600
Proceeds from sale of Storage Assets	$ 24,395	0
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of transactions involved in sale of business | transaction	3
Number of buyers involved in sale of business | buyer	3
Proceeds from sale of Storage Assets	$ 24,400
Gain on sale of business, net of tax	3,100
Shred-it | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investments	194,300		$ 210,100
Difference between carrying amount and underlying equity in net assets	$ 91,200
Amortization period of basis difference	9 years
Loss on investment in Shred-it, net of tax	$ 9,300
Amortization of basis difference	$ 2,800
Gain on sale of stock of an equity method investment, net of tax		$ 3,900