Summary of Significant Accounting Policies - Narrative (Details) ft² in Millions		12 Months Ended
	Jan. 01, 2019 USD ($)	Dec. 31, 2019 USD ($) ft² land_parcel reporting_unit state property	Dec. 31, 2018 USD ($) property	Dec. 31, 2017 USD ($) property
Business Overview [Abstract]
Gross investment, amount, total		$ 4,400,000,000
Real estate properties and mortgages | property		204
Number of owned real estate properties | property		204
Number of states that the Company owns real estate in | state		25
Square footage of owned real estate properties | ft²		15.4
Approximate square feet for which Nationwide property management services provided by company | ft²		11.4
Segment Reporting [Abstract]
Number of Reporting Units | reporting_unit		1
Real Estate Properties [Abstract]
Total real estate properties		$ 4,359,993,000	$ 3,974,071,000
Elimination of real estate lease intangibles against accumulated depreciation		28,000,000.0	23,200,000
Depreciation		$ 152,600,000	143,800,000	$ 129,400,000
Maximum period up to which interest capitalize on properties in stabilization		1 year
Land Held for Development [Abstract]
Number of land parcels held for development | land_parcel		7
Land held for development		$ 24,600,000	24,600,000
Goodwill and Intangible Assets [Abstract]
Goodwill impairment loss		0	0
Goodwill		3,500,000	$ 3,487,000
Other Operating Income [Abstract]
Number of owned real estate properties to which property operating agreements between company and sponsoring health system is applicable | property			1	1
Federal Income Taxes [Abstract]
Provision for federal income tax		$ 0
Percentage of distribution of taxable income for qualify as REIT		90.00%
Lease liabilities		$ 91,574,000
Maximum [Member]
Federal Income Taxes [Abstract]
Ground lease, initial term		99 years	75 years
Minimum [Member]
Federal Income Taxes [Abstract]
Ground lease, initial term		40 years	50 years
Other Assets [Member]
Federal Income Taxes [Abstract]
Transfers to operating lease, right-of-use assets	$ 45,000,000.0
Other Liabilities [Member]
Federal Income Taxes [Abstract]
Transfers to operating lease, right-of-use assets	1,900,000
Accounts Payable and Accrued Liabilities [Member]
Federal Income Taxes [Abstract]
Transfers to operating lease, right-of-use assets	8,400,000
Forward Starting Interest Rate Swap [Member]
Derivative Instrument Detail [Abstract]
Accumulated other comprehensive income (loss), net of tax		$ 6,200,000	$ 900,000
Tenant and Capital Improvements [Member]
Real Estate Properties [Abstract]
Fully depreciated tenant and capital improvements eliminated against accumulated depreciation		1,300,000	500,000
At Market Lease Intangibles [Member]
Real Estate Properties [Abstract]
Elimination of real estate lease intangibles against accumulated depreciation		$ 17,200,000	$ 9,900,000
Accounting Standards Update 2016-02 [Member]
Federal Income Taxes [Abstract]
Lease liabilities	$ 91,700,000
Accounting Standards Update 2016-02 [Member] | Maximum [Member]
Federal Income Taxes [Abstract]
Ground lease, initial term		52 years 1 month 6 days
Operating lease, discount rate (percent)			6.20%
Ground lease, discount rate			6.20%
Accounting Standards Update 2016-02 [Member] | Minimum [Member]
Federal Income Taxes [Abstract]
Operating lease, discount rate (percent)			3.80%
Ground lease, discount rate			3.80%