SEGMENT INFORMATION - Schedule of Assets by Region (Details) - USD ($) $ in Thousands	Dec. 31, 2016	May 31, 2016	May 31, 2015
Segment Reporting Information [Line Items]
Long-lived assets, excluding goodwill and other intangible assets	$ 526,370	$ 493,678	$ 374,143
United States
Segment Reporting Information [Line Items]
Long-lived assets, excluding goodwill and other intangible assets	413,499	394,716	284,257
Foreign countries
Segment Reporting Information [Line Items]
Long-lived assets, excluding goodwill and other intangible assets	$ 112,871	$ 98,962	$ 89,886