Dispositions of Real Estate and Discontinued Operations - 2018 Other Dispositions (Details) $ in Thousands	1 Months Ended		3 Months Ended				12 Months Ended
	Mar. 31, 2017 USD ($) facility	Jan. 31, 2017 USD ($) facility	Dec. 31, 2018 USD ($) facility	Sep. 30, 2018 USD ($) facility	Jun. 30, 2018 USD ($) facility	Mar. 31, 2018 USD ($) facility	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) facility	Dec. 31, 2016 USD ($) facility
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sales of real estate, net				$ 95,000	$ 25,000		$ 925,985	$ 356,641	$ 164,698
SHOP
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed (in facilities) | facility			2	11	8	2		5	3
Proceeds from sale of real estate			$ 15,000	$ 76,000	$ 268,000	$ 35,000
Gain (loss) on sales of real estate, net						$ 21,000
Medical office
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed (in facilities) | facility			2	2				4	3
Proceeds from sale of real estate			$ 4,000	$ 21,000
Gain (loss) on sales of real estate, net								$ 41,000
Senior housing triple-net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed (in facilities) | facility	64				2			4	7
Proceeds from sale of real estate					$ 35,000
Gain (loss) on sales of real estate, net	$ 170,000
Life science
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed (in facilities) | facility		4		4					5
Proceeds from sale of real estate				$ 269,000
Gain (loss) on sales of real estate, net		$ 45,000
Land | Life science
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed (in facilities) | facility			1
Proceeds from sale of real estate			$ 3,000