BUSINESS ACQUISITIONS - Accurate Rx Pharmacy Consulting, LLC (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Jul. 05, 2017	Jul. 03, 2017	Nov. 30, 2018	Dec. 31, 2017	Dec. 31, 2018	May 08, 2017	Dec. 31, 2016	Dec. 31, 2014
Summary of the preliminary fair value determination of the acquired assets and liabilities
Definite-lived intangible assets						$ 7,730
Goodwill				$ 832,624	$ 609,592		$ 316,616	$ 256,318
Accurate Rx Pharmacy Consulting, LLC
BUSINESS ACQUISITIONS
Cash	$ 9,408
Restricted common shares	1,776
Contingent consideration at fair value	1,980		$ 1,800
Total	$ 13,164
Restricted common shares (in shares)	131,108
Market price (in dollars per share)		$ 15.05
Market price multiplier to factor in restricted nature of the shares (as a percent)		90.00%
Maximum additional cash payouts per performance period	$ 3,600
Maximum payout of contingent consideration	7,200
Fair value of contingent liability				1,600	$ 1,715
Purchase consideration deposited into an escrow account	$ 1,000
Deposit term into an escrow account	15 months
Acquisition-related costs charged to Selling, general, and administrative expenses				$ 218
Summary of the preliminary fair value determination of the acquired assets and liabilities
Cash	$ 1,295
Accounts receivable	2,196
Inventory	936
Prepaid expenses and other current assets	34
Definite-lived intangible assets	3,420
Other noncurrent assets	3
Accounts payable	(3,303)
Accrued expenses - compensation and benefits	(152)
Accrued expenses - other	(6)
Total identifiable net assets	4,423
Goodwill	8,741
Total acquisition price	13,164
Patient relationships | Accurate Rx Pharmacy Consulting, LLC
Summary of the preliminary fair value determination of the acquired assets and liabilities
Definite-lived intangible assets	$ 2,100
Definite-lived intangible assets
Useful Life	7 years
Non-compete employment agreements | Accurate Rx Pharmacy Consulting, LLC
Summary of the preliminary fair value determination of the acquired assets and liabilities
Definite-lived intangible assets	$ 670
Definite-lived intangible assets
Useful Life	5 years
Trade names and trademarks | Accurate Rx Pharmacy Consulting, LLC
Summary of the preliminary fair value determination of the acquired assets and liabilities
Definite-lived intangible assets	$ 650
Definite-lived intangible assets
Useful Life	4 years