Summary of Significant Accounting Policies (Details) $ in Thousands		3 Months Ended
	Jan. 01, 2018 USD ($)	Mar. 31, 2019 USD ($) facility	Mar. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)		Dec. 31, 2018 USD ($)		Dec. 31, 2017 USD ($)	[2]	Mar. 31, 2017
Schedule of Equity Method Investments [Line Items]
Cumulative effect adjustment to equity		$ 5,836,882				$ 5,944,439
Cumulative effect of new accounting principle						590	[1]	$ 79,144
Present value of lease liabilities		152,837				0
Right-of-use asset		165,748				$ 0
RIDEA II
Schedule of Equity Method Investments [Line Items]
Investment ownership percentage										40.00%
Equity method investments	$ 121,000
ASU 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Schedule of Equity Method Investments [Line Items]
Cumulative effect adjustment to equity	79,000
Impairment charge	30,000
ASU 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | RIDEA II
Schedule of Equity Method Investments [Line Items]
Fair value of equity method investments	$ 107,000
ASU 2016-02
Schedule of Equity Method Investments [Line Items]
Present value of lease liabilities				$ 153,000
Right-of-use asset				166,000
Accrued straight-line rent liability				20,000
Unamortized lease intangibles				33,000
Ancillary service revenue | ASU 2014-09
Schedule of Equity Method Investments [Line Items]
Tenant recoveries and Resident fees and services		$ 10,000	$ 10,000
Tenant recoveries
Schedule of Equity Method Investments [Line Items]
Rental and related revenues			$ 37,000
Medical office
Schedule of Equity Method Investments [Line Items]
Number of facilities transitioned | facility		2
Cumulative Dividends In Excess Of Earnings
Schedule of Equity Method Investments [Line Items]
Cumulative effect of new accounting principle				$ 590	[1]			$ 79,144

[1] On January 1, 2019, the Company adopted a series of Accounting Standards Updates (“ASUs”) related to accounting for leases, and recognized the cumulative-effect of adoption to beginning retained earnings. Refer to Note 2 for a detailed impact of adoption.

[2] On January 1, 2018, the Company adopted ASU No. 2017-05, Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets (“ASU 2017-05”), and recognized the cumulative-effect of adoption to beginning retained earnings. Refer to Note 2 for a detailed impact of adoption.