Stock-Based Compensation - Stock Options (Details) shares in Thousands	12 Months Ended
	May 31, 2016 $ / shares shares
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	2,096
Weighted-Average Remaining Contractual Life in Years	6 years 8 months 12 days
Weighted-Average Exercise Price (in dollars per Share)	$ 22.17
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	837
Weighted-Average Exercise Price (in dollar per Share)	$ 21.21
$10.00 - $15.00
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	10.00
Option Exercise Price Range, high end of range (in dollars per share)	$ 15.00
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	505
Weighted-Average Remaining Contractual Life in Years	6 years 1 month 6 days
Weighted-Average Exercise Price (in dollars per Share)	$ 12.90
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	202
Weighted-Average Exercise Price (in dollar per Share)	$ 12.90
$15.01 - $20.00
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	15.01
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	213
Weighted-Average Remaining Contractual Life in Years	3 years 7 months 6 days
Weighted-Average Exercise Price (in dollars per Share)	$ 16.75
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	208
Weighted-Average Exercise Price (in dollar per Share)	$ 16.75
$20.01 - $34.50
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)	$ 34.50
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	1,378
Weighted-Average Remaining Contractual Life in Years	7 years 4 months 24 days
Weighted-Average Exercise Price (in dollars per Share)	$ 26.40
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	427
Weighted-Average Exercise Price (in dollar per Share)	$ 27.32