STOCKHOLDERS' EQUITY - Capital Stock (Details) - USD ($) $ in Thousands	1 Months Ended	7 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Issuance of common stock, shares	3,750,202	2,075,708
Proceeds for the issuance of common stock	$ 285,400	$ 132,700	$ 417,818	$ 242,107
Sales agent commissions for common stock sales	$ 4,400	2,000
Common stock reserved for future issuance, amount (up to $1.0 Billion)		$ 1,000,000	1,000,000
Common Stock
Business Acquisition [Line Items]
Proceeds for the issuance of common stock			$ 1,457	$ 845
American Realty Capital Healthcare Trust | Common Stock
Business Acquisition [Line Items]
Equity interest issued, number of shares	28,400,000
American Realty Capital Healthcare Trust | Limited Partnership Units
Business Acquisition [Line Items]
Equity interest issued, number of shares	1,100,000