DESCRIPTION OF BUSINESS (Details) $ / shares in Units, $ in Thousands	1 Months Ended		9 Months Ended
	Mar. 31, 2015 USD ($) $ / shares shares	Oct. 31, 2014 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) segment location $ / shares	Sep. 30, 2014 USD ($) $ / shares	Dec. 31, 2014 $ / shares
DESCRIPTION OF BUSINESS
Number of pharmacy locations | location			16
Number of reportable segments | segment			1
Initial Public Offering [Line Items]
Public offering price (in dollars per share) | $ / shares				$ 13.00
Proceeds from follow-on public offering, net of transaction costs			$ 187,238
Other offering expenses				$ 1,368
Number of newly authorized shares issued upon conversion (in shares) | shares		1
Common shares, par value (in dollars per share) | $ / shares		$ 0.00	$ 0.00		$ 0.00
Borrowings under the revolving line of credit			$ 21,756
Initial Public Offering
Initial Public Offering [Line Items]
Number of shares of common stock sold (in shares) | shares		15,333,333
Number of shares sold by the Company (in shares) | shares		11,000,000
Number of shares of stock sold by the existing shareholders (in shares) | shares		4,333,333
Public offering price (in dollars per share) | $ / shares		$ 13.00
Net proceeds from initial public offering		$ 130,440
Underwriting discounts and commissions		9,652
Other offering expenses		2,908
Net proceeds used for debt payments		80,458
Existing indebtedness to certain current or former shareholders and employees		19,824
Amount of borrowings repaid under the revolving line of credit		$ 60,634
Follow-On Public Offering
Initial Public Offering [Line Items]
Number of shares of common stock sold (in shares) | shares	9,821,125
Number of shares sold by the Company (in shares) | shares	6,821,125
Number of shares of stock sold by the existing shareholders (in shares) | shares	3,000,000
Public offering price (in dollars per share) | $ / shares	$ 29.00
Proceeds from follow-on public offering, net of transaction costs	$ 187,238
Underwriting discounts and commissions	9,891
Other offering expenses	685
Net proceeds used to repurchase stock options	$ 36,298