Acquisitions, Dispositions and Other Significant Transactions (Details) $ in Thousands			3 Months Ended				6 Months Ended		12 Months Ended	18 Months Ended
	Mar. 29, 2017 community	Nov. 01, 2016 community	Jun. 30, 2017 USD ($)	Mar. 31, 2017 community	Dec. 31, 2016 community	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) community	Jun. 30, 2016 USD ($)	Dec. 31, 2016 community	Jun. 30, 2017 USD ($) community
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of					7
Resident fee revenue | $			$ 934,070			$ 1,054,568	$ 1,950,997	$ 2,115,716
Facility operating expenses | $			642,405			693,103	1,316,947	1,409,005
Cash lease payments | $			90,599			96,031	185,203	191,611
Loss on facility lease termination | $			6,368			0	6,368	0
Number of communities contributed to joint venture		4
130 Communities Disposed Of By Sales And Lease Terminations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of										130
Resident fee revenue | $			6,300			116,200	82,300	236,100
Facility operating expenses | $			7,500			88,500	62,900	177,000
Cash lease payments | $			600			26,400	$ 23,700	52,400
16 Communities Held For Sale [Member] | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of							3
Number of communities classified as held for sale				1					16
Additional communities disposed of in agreement				1
Number of community leases terminated							8
16 Communities Held For Sale [Member] | Assisted Living [Member] | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Additional communities disposed of in agreement							8
16 Communities Held For Sale [Member] | CCRCs Rental [Member] | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Additional communities disposed of in agreement							3
14 Communities Held For Sale [Member] | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Resident fee revenue | $			9,400			9,700	$ 18,900	19,700
Facility operating expenses | $			7,900			8,100	$ 15,600	16,300
Number of communities classified as held for sale							14
Assets held for sale | $			91,000				$ 91,000			$ 91,000
14 Communities Held For Sale [Member] | Long-term Debt [Member] | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long term mortgage debt | $			60,500				$ 60,500			$ 60,500
14 Communities Held For Sale [Member] | Assisted Living [Member] | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Additional communities disposed of in agreement							12
14 Communities Held For Sale [Member] | CCRCs Rental [Member] | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Additional communities disposed of in agreement							2
Termination Of Triple Net Leases [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of		97
Termination Of 25 Triple Net Leases [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of							25
Resident fee revenue | $			18,600			18,500	$ 36,900	36,500
Facility operating expenses | $			15,000			14,600	29,900	29,400
Cash lease payments | $			$ 2,800			$ 4,900	$ 5,500	$ 9,800
Termination Of 25 Triple Net Leases [Member] | Assisted Living [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of							23
Termination Of 25 Triple Net Leases [Member] | CCRCs Rental [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of							2
Termination Of 8 Triple Net Leases [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of							8
Termination Of 8 Triple Net Leases [Member] | Assisted Living [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of							6
Termination Of 8 Triple Net Leases [Member] | Retirement Centers [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of							1
Termination Of 8 Triple Net Leases [Member] | CCRCs Rental [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities disposed of							1
Blackstone Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities acquired		64
HCP, Inc. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of communities contributed to joint venture					4		4
HCP, Inc. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage ownership			10.00%				10.00%			10.00%
Joint Venture [Member] | Blackstone Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of community leases terminated	62
Percentage ownership	15.00%		15.00%				15.00%			15.00%
Joint Venture [Member] | Blackstone Venture [Member] | Assisted Living [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of community leases terminated	47
Joint Venture [Member] | Blackstone Venture [Member] | Retirement Centers [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of community leases terminated	8
Joint Venture [Member] | Blackstone Venture [Member] | CCRCs Rental [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of community leases terminated	7