Discontinued Operations - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	May 31, 2015 USD ($)	May 31, 2016 USD ($)	May 31, 2017 USD ($)	May 31, 2016 USD ($)	May 31, 2015 USD ($) transaction buyer
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investments		$ 14,500	$ 15,800	$ 14,500
Dividends received on equity method investment			0	0	$ 5,247
Gain (loss) on Shred-it			25,457	354,071	(3,851)
Proceeds from Shredding transactions, net of cash contributed			25,876	580,837	3,344
Income tax expense			1,460	15,786	38,573
Proceeds from Storage transactions, net of cash contributed			2,400	35,338	158,428
Discontinued Operations | Storage Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on Shred-it			25,457	354,071	(3,851)
Income tax expense			2,400	15,786	38,573
Proceeds from Storage transactions, net of cash contributed					$ 158,400
Realized gain as a result of contingent consideration received				10,900
Discontinued Operations, Held-for-sale | Storage Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense				4,800
Proceeds from Storage transactions, net of cash contributed				24,400
Number of transactions involved in sale of business | transaction					3
Number of buyers involved in sale of business | buyer					3
Shred-it Partnership
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investments	$ 210,100				$ 210,100
Dividends received on equity method investment	113,400		0	0	113,400
Equity method investment, difference between carrying amount and underlying net assets	$ 94,000				$ 94,000
Amortization period					9 years
Equity method investment net gain (loss)			24,300		$ 5,500
Amortization of basis difference			4,800		11,000
Gain (loss) on Shred-it					4,100
Litigation settlement expense					$ 1,000
Proceeds from Shredding transactions, net of cash contributed				$ 578,300
Income tax expense		$ 4,300	$ 25,500