Real Estate Transactions - Disposition of Real Estate (Details) $ in Thousands	1 Months Ended		3 Months Ended								9 Months Ended
	Oct. 31, 2018 USD ($)	Mar. 31, 2017 USD ($) property	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($) facility	Jun. 30, 2018 USD ($) facility	Mar. 31, 2018 USD ($) facility	Dec. 31, 2017 USD ($) facility	Sep. 30, 2017 USD ($) facility	Jun. 30, 2017 USD ($) facility	Mar. 31, 2017 USD ($) facility	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sales of real estate, net				$ 95,332	$ 25,000		$ 34,000	$ 5,182	$ 1,000	$ 45,000	$ 162,211	$ 322,852
SHOP
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | facility				11	8	2	4			1
Total consideration for disposal of real estate				$ 76,000	$ 268,000	$ 35,000	$ 41,000			$ 3,000
Gain (loss) on sales of real estate, net						$ 21,000
Senior housing triple-net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed		64			2		2	2
Total consideration for disposal of real estate		$ 1,125,000			$ 35,000		$ 12,000	$ 15,000
Gain (loss) on sales of real estate, net		$ 170,000						$ 5,000
Life science
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | facility				4					1	4
Total consideration for disposal of real estate				$ 269,000					$ 5,000	$ 76,000
Medical office
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | facility				2			3
Total consideration for disposal of real estate				$ 21,000			$ 14,000
Land
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | facility									1
Total consideration for disposal of real estate									$ 27,000
Forecast | Life science
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total consideration for disposal of real estate			$ 1,000,000
Gain (loss) on sales of real estate, net			$ 700,000
Subsequent Event | Life science
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Nonrefundable deposits on real estate sales	$ 65,000