ACQUISITIONS OF REAL ESTATE PROPERTY - Narrative (Details) $ / shares in Units, $ in Thousands		1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 04, 2015 USD ($) hospital	Aug. 31, 2015 property	Jan. 31, 2015 USD ($) property $ / shares shares	Aug. 31, 2014 CAD property	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) property	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) property shares	Jul. 31, 2014 CAD	Aug. 31, 2004 CAD
Business Acquisition [Line Items]
Amount paid for equity interest							$ 26,282	$ 0
Total net real estate property					$ 19,771,586		19,771,586		$ 16,754,254
Goodwill					1,052,321		1,052,321		$ 363,971
Revenues					827,606	$ 704,932	2,445,124	2,044,723
Acquisition-related costs					62,145	16,188	105,023	35,944
Triple-Net Leased Properties
Business Acquisition [Line Items]
Revenues					202,039	172,009	574,877	503,476
Senior Living Operations
Business Acquisition [Line Items]
Revenues					454,825	396,247	1,356,384	1,141,781
MOB Operations
Business Acquisition [Line Items]
Revenues					151,214	$ 122,623	445,353	360,253
Ardent
Business Acquisition [Line Items]
Percentage of investment in acquisition	9.90%
2015 Acquisitions
Business Acquisition [Line Items]
Total cash used							2,592,169
Assumed mortgage debt					177,857		177,857
Goodwill					746,500		746,500
Revenues							223,000
NOI							132,300
2015 Acquisitions | Merger-Related Expenses and Deal Costs
Business Acquisition [Line Items]
Acquisition-related costs							96,900	5,400
2015 Acquisitions | Discontinued Operations
Business Acquisition [Line Items]
Acquisition-related costs							4,000	$ 800
2015 Acquisitions | Triple-Net Leased Properties
Business Acquisition [Line Items]
Assumed mortgage debt					0		0
Goodwill					133,500		133,500
2015 Acquisitions | Senior Living Operations
Business Acquisition [Line Items]
Assumed mortgage debt					77,940		77,940
Goodwill					219,700		219,700
2015 Acquisitions | MOB Operations
Business Acquisition [Line Items]
Assumed mortgage debt					99,917		99,917
Goodwill					393,400		$ 393,400
Ardent
Business Acquisition [Line Items]
Estimated fair value of investment	$ 1,300,000
Number of hospitals acquired | hospital	10
Ardent | Ardent
Business Acquisition [Line Items]
Amount paid for equity interest	$ 26,300
American Realty Capital Healthcare Trust
Business Acquisition [Line Items]
Number of real estate properties acquired | property			152
Consideration transferred, stock conversion ratio, per acquiree share			0.1688
Consideration transferred, price per acquiree share | $ / shares			$ 11.33
Total cash used			$ 11,000
Assumed mortgage debt			167,000
Repayments of debt			$ 730,000
American Realty Capital Healthcare Trust | CCP Spin-Off
Business Acquisition [Line Items]
Number of real estate properties acquired and contributed in the spin-off | property		20
American Realty Capital Healthcare Trust | Common Stock Par Value
Business Acquisition [Line Items]
Equity interest issued, number of shares | shares			28,400,000
American Realty Capital Healthcare Trust | Limited Partnership Units
Business Acquisition [Line Items]
Equity interest issued, number of shares | shares			1,100,000
2015 Development Projects | Seniors Housing Communities
Business Acquisition [Line Items]
Number of real estate properties completed | property							1
Total net real estate property					$ 7,800		$ 7,800
Other Acquisitions
Business Acquisition [Line Items]
Equity interest issued, number of shares | shares									148,241
Other investments									$ 812,000
Payment for early repayment of debt at closing									$ 18,800
Other Acquisitions | Triple-Net Leased Properties
Business Acquisition [Line Items]
Other investments							$ 514,000
Other Acquisitions | Seniors Housing Communities And Hospitals | Triple-Net Leased Properties
Business Acquisition [Line Items]
Number of real estate properties acquired | property							11
Other Acquisitions | Seniors Housing Communities | Triple-Net Leased Properties
Business Acquisition [Line Items]
Number of real estate properties acquired | property									26
Other Acquisitions | Seniors Housing Communities | Senior Living Operations
Business Acquisition [Line Items]
Number of real estate properties acquired | property									4
Other Acquisitions | Private Hospitals | Triple-Net Leased Properties
Business Acquisition [Line Items]
Number of real estate properties acquired | property									3
Other Acquisitions | Skilled Nursing Facilities | Triple-Net Leased Properties
Business Acquisition [Line Items]
Number of real estate properties acquired | property							12
Other Acquisitions | Skilled Nursing Facilities | MOB Operations
Business Acquisition [Line Items]
Number of real estate properties acquired | property							1
Holiday Retirement
Business Acquisition [Line Items]
Assumed mortgage debt | CAD											CAD 193,700,000
Other investments | CAD				CAD 957,000,000
Payment for early repayment of debt at closing | CAD				CAD 26,900,000
Holiday Retirement | Unsecured Term Loan | Unsecured Term Loan Due 2015
Business Acquisition [Line Items]
Loan amount | CAD										CAD 791,000,000.0
Holiday Retirement | Seniors Housing Communities
Business Acquisition [Line Items]
Number of real estate properties acquired | property				29
2014 Development Projects
Business Acquisition [Line Items]
Total net real estate property									$ 41,200
2014 Development Projects | Seniors Housing Communities
Business Acquisition [Line Items]
Number of real estate properties completed | property									1
2014 Development Projects | Medical Office Buildings
Business Acquisition [Line Items]
Number of real estate properties completed | property									2