Stock-Based Compensation - Stock Options (Details) shares in Thousands	12 Months Ended
	May 31, 2018 $ / shares shares
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	2,082
Weighted-Average Remaining Contractual Life in Years	7 years
Weighted-Average Exercise Price (in dollars per Share)	$ 26.72
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	883
Weighted-Average Exercise Price (in dollar per Share)	$ 23.81
$12.00 - $20.00
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	12.00
Option Exercise Price Range, high end of range (in dollars per share)	$ 20.00
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	160
Weighted-Average Remaining Contractual Life in Years	3 years 2 months 12 days
Weighted-Average Exercise Price (in dollars per Share)	$ 14.51
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	160
Weighted-Average Exercise Price (in dollar per Share)	$ 14.51
$20.01 - $26.00
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	20.01
Option Exercise Price Range, high end of range (in dollars per share)	$ 26.00
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	1,041
Weighted-Average Remaining Contractual Life in Years	6 years 9 months 18 days
Weighted-Average Exercise Price (in dollars per Share)	$ 24.63
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	447
Weighted-Average Exercise Price (in dollar per Share)	$ 24.93
$26.01 - $38.70
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	26.01
Option Exercise Price Range, high end of range (in dollars per share)	$ 38.70
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	881
Weighted-Average Remaining Contractual Life in Years	7 years 10 months 24 days
Weighted-Average Exercise Price (in dollars per Share)	$ 31.41
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	276
Weighted-Average Exercise Price (in dollar per Share)	$ 27.37