Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2019	Jan. 01, 2018	Jan. 31, 2017
Accounting Policies [Abstract]
Residency agreement term, minimum	30 days
Residency agreement term, maximum	1 year
Maximum period available for occupancy from cessation of significant construction activity	1 year
Maximum useful life of building and improvements	60 years
Schedule of Equity Method Investments [Line Items]
HCP’s capital	$ 5,944,439	$ 5,301,005
RIDEA II
Schedule of Equity Method Investments [Line Items]
Investment ownership percentage	40.00%					40.00%
Fair value of equity investment						$ 107,000
Equity method investments	$ 0	259,651				$ 121,000
ASU 2014-09
Schedule of Equity Method Investments [Line Items]
HCP’s capital					$ 79,000
Difference between Revenue Guidance in Effect before and after Topic 606 | ASU 2014-09
Schedule of Equity Method Investments [Line Items]
Cumulative effect of change on beginning retained earnings					$ 30,000
Ancillary Service Revenue | ASU 2014-09
Schedule of Equity Method Investments [Line Items]
Lease revenue	40,000	38,000	$ 51,000
Rental and related revenues, tenant recoveries
Schedule of Equity Method Investments [Line Items]
Lease revenue	$ 157,000	$ 142,000	$ 134,000
Forecast | Minimum | ASU 2016-02
Schedule of Equity Method Investments [Line Items]
Lease liabilities				$ 130,000
Right-of-use asset				145,000
Forecast | Maximum | ASU 2016-02
Schedule of Equity Method Investments [Line Items]
Lease liabilities				165,000
Right-of-use asset				$ 180,000