Real Estate Transactions - Disposition of Real Estate (Details) $ in Thousands	1 Months Ended				3 Months Ended
	Apr. 30, 2018 USD ($) facility	Jan. 31, 2018 USD ($) facility	Mar. 31, 2017 USD ($) property	Jan. 31, 2017 USD ($) facility	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sales of real estate, net					$ 20,815	$ 317,258
SHOP
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | facility		2
Total consideration for disposal of real estate		$ 35,000
Gain (loss) on sales of real estate, net		$ 21,000
SHOP | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | facility	4
Senior housing triple-net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | property			64
Total consideration for disposal of real estate			$ 1,125,000
Gain (loss) on sales of real estate, net			$ 170,000
Senior housing triple-net | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | facility	2
Triple-net and SHOP | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total consideration for disposal of real estate	$ 265,000
Life science
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | facility				4
Total consideration for disposal of real estate				$ 76,000
Gain (loss) on sales of real estate, net				$ 45,000