Acquisitions, Dispositions and Other Significant Transactions (Details) $ in Thousands			3 Months Ended			12 Months Ended	15 Months Ended
	Mar. 29, 2017 community	Nov. 01, 2016 community	Mar. 31, 2017 USD ($) community	Dec. 31, 2016 community	Mar. 31, 2016 USD ($) community	Dec. 31, 2016 community	Mar. 31, 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 | $			$ 1,016,927		$ 1,061,148
Facility operating expenses | $			674,542		715,902
Cash lease payments | $			$ 94,604		95,580
Number of communities contributed to joint venture		4
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 classified as held for sale			16			16
Number of communities disposed of			1
Additional communities disposed of in agreement			1
Assets held for sale | $			$ 106,300				$ 106,300
Resident fee revenue | $			13,800		14,200
Facility operating expenses | $			11,900		12,500
16 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
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]
Number of communities classified as held for sale						13
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]
Number of communities classified as held for sale						3
59 Communities Disposed Of By Sale Or Lease Terminations [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							59
Resident fee revenue | $			700		43,500
Facility operating expenses | $			$ 1,300		33,800
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 | $			$ 18,400		18,000
Facility operating expenses | $			14,900		14,800
Cash lease payments | $			$ 2,700		$ 4,900
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		8
Resident fee revenue | $					$ 11,400
Facility operating expenses | $					8,000
Cash lease payments | $					$ 3,000
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] | CCRCs Rental [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] | Retirement Centers [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%
Joint Venture [Member] | Blackstone Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Resident fee revenue | $			$ 64,000		$ 65,200
Facility operating expenses | $			$ 43,900		$ 44,100
Number of community leases terminated	62		62		62
Cash lease payments | $			$ 22,200		$ 21,300
Percentage ownership	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] | CCRCs Rental [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of community leases terminated			7
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