GOODWILL AND DEFINITE-LIVED INTANGIBLE ASSETS - Goodwill Rollforward by reporting segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Acquired Intangible Assets
Goodwill	$ 841,502		$ 841,502	$ 834,558
Accumulated impairment losses	(469,933)		(469,933)	(224,966)
Balance as of beginning of period			609,592
Impairment losses	(122,076)	$ (122,891)	(244,967)
Other			(138)
Balance as of end of period	371,569		371,569
InTouch Pharmacy LLC
Acquired Intangible Assets
Goodwill acquired during the period			7,082
PBM
Acquired Intangible Assets
Goodwill	447,984		447,984	448,122
Accumulated impairment losses	(355,939)		(355,939)	(179,190)
Balance as of beginning of period			268,932
Impairment losses	(122,076)	(54,673)
Other			(138)
Balance as of end of period	92,045		92,045
Specialty
Acquired Intangible Assets
Goodwill	393,518		393,518	386,436
Accumulated impairment losses	(113,994)		(113,994)	$ (45,776)
Balance as of beginning of period			340,660
Impairment losses		$ (68,218)
Balance as of end of period	$ 279,524		279,524
Specialty | InTouch Pharmacy LLC
Acquired Intangible Assets
Goodwill acquired during the period			$ 7,082