ACQUISITIONS AND DISPOSITION OF ASSETS - Fair Value of Acquired Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Sep. 01, 2017
Allocated fair value of acquired assets and assumed liabilities
Goodwill	$ 2,021,970	$ 2,124,033
Bonten
Allocated fair value of acquired assets and assumed liabilities
Accounts receivable			$ 14,536
Prepaid expenses and other current assets			699
Program contract costs			988
Property and equipment			27,295
Definite-lived intangible assets			161,936
Indefinite-lived intangible assets			425
Other assets			3,609
Accounts payable and accrued liabilities			(8,846)
Program contracts payable			988
Deferred tax liability			(66,158)
Other long term liabilities			(12,156)
Fair value of identifiable net assets acquired			121,340
Goodwill			120,812
Total purchase price, net of cash acquired			$ 242,152