Dispositions of Real Estate and Discontinued Operations - 2017 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 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]
Proceeds from sales of real estate							$ 2,044,477	$ 1,314,325	$ 647,754
Gain (loss) on sales of real estate, net				$ 95,000	$ 25,000		$ 925,985	356,641	$ 164,698
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
Total consideration for disposition of real estate		$ 76,000							$ 386,000
Gain (loss) on sales of real estate, net		$ 45,000
Life science | Land
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed (in facilities) | facility			1
Total consideration for disposition of real estate								27,000
Life science | Building
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sales of real estate								$ 5,000
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
Total consideration for disposition of real estate									$ 20,000
Proceeds from sales of real estate								$ 15,000
Gain (loss) on sales of real estate, net								$ 41,000
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
Total consideration for disposition of real estate									$ 41,000
Proceeds from sales of real estate								$ 43,000
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 (in facilities) | facility	64				2			4	7
Total consideration for disposition of real estate	$ 1,125,000								$ 88,000
Proceeds from sales of real estate								$ 27,000
Gain (loss) on sales of real estate, net	$ 170,000
Senior housing triple-net | Building
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed (in facilities) | facility									2