Employee Benefit Plans - Narrative (Details) - USD ($)	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Estimated contribution to pension plan	$ 0
Accrued benefit liability	28,000,000
Unrecognized net actuarial loss	1,200,000
Fair value of plan assets	59,396,000	$ 0
Projected benefit obligation	87,387,000	0
Net periodic benefit cost	$ (28,000)
Expected return on plan assets (as a percent)	5.40%
Supplemental Executive Retirement Plan (SERP)
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 6,900,000	6,600,000	$ 6,100,000
Domestic Plan
Defined Benefit Plan Disclosure [Line Items]
Required years of service for plan eligibility (years)	1 year
Employer contributions	$ 47,500,000	43,100,000	38,400,000
Deferred Profit Sharing Plan (DPSP)
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	1,800,000	1,600,000	$ 1,500,000
Pension Plan of Immaterial Acquisitions
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,100,000	6,500,000
Projected benefit obligation	7,500,000	7,700,000
Net periodic benefit cost	$ 100,000	$ 100,000