Fair Value Measurements - Narrative (Details) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
	Jul. 26, 2020 USD ($) $ / shares shares	Mar. 31, 2018 USD ($)	Dec. 31, 2020 USD ($) community lease	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2020 USD ($) community	Jun. 30, 2020 USD ($) community	Mar. 31, 2020 USD ($) community	Jan. 01, 2019 USD ($) community	Dec. 31, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities			$ 172,905	$ 68,567
Debt			3,915,988	3,555,123
Goodwill			$ 154,131	154,131
Number of communities leased | lease			235
Cumulative effect of change in accounting principle			$ 802,729	698,725	$ 1,018,413					$ 1,530,291
Accumulated Deficit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative effect of change in accounting principle			$ (3,311,184)	(3,393,088)	(3,069,272)					(2,541,294)
Cumulative Effect, Period of Adoption, Adjustment | Accumulated Deficit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative effect of change in accounting principle				(115)	(55,885)					$ 0
Condensed Consolidated Balance Sheet
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of communities leased | community			5			2	9	35	25
Estimated fair value			$ 2,300			$ 3,000	$ 10,300	$ 106,700	$ 56,600
Ventas, Inc | The Warrant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of shares authorized to be purchased | shares	16,300,000
Share price (in usd per share) | $ / shares	$ 3.00
Issuance of warrants	$ 22,900
Volatility rate	65.00%
Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt			3,900,000	3,600,000
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities			172,900
Assisted Living and Memory Care
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of carrying amount in excess of fair value		$ 351,700
Goodwill impairment		$ 351,700
Goodwill			0
Independent Living
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill			27,321
Health Care Services
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill			126,810	126,800
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment			0	0	351,700
Property, plant and equipment impairment			29,300	27,200	78,000
Operating lease right-of-use assets			76,300	10,200	0
Equity method investment impairment			1,500	0	33,400
Impairment of assets held for sale			$ 200	1,300	15,600
Non-cash impairment charge				$ 7,600	$ 9,100
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate			9.00%
Minimum | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Capitalization rate			6.50%
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate			12.30%
Maximum | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Capitalization rate			9.00%
ASU 2016-02
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative effect of change in accounting principle									(56,000)
ASU 2016-02 | Cumulative Effect, Period of Adoption, Adjustment | Accumulated Deficit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative effect of change in accounting principle									$ 58,100