Subsequent Events - Narrative (Details) $ / shares in Units, shares in Thousands				1 Months Ended	2 Months Ended	3 Months Ended				12 Months Ended
	Feb. 08, 2019 USD ($)	Nov. 18, 2016 USD ($) shares	Mar. 28, 2016 USD ($) shares	Jan. 31, 2019 USD ($) $ / shares shares	Feb. 13, 2019 USD ($) extension_option facility campus	Dec. 31, 2018 USD ($) $ / shares shares	Sep. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) property $ / shares shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 27, 2019 USD ($) facility company campus
Subsequent Event [Line Items]
Issuance of common stock, net (shares) | shares		6,330	9,780
Proceeds from the issuance of common stock, net		$ 80,900,000	$ 105,800,000							$ 179,882,000	$ 170,323,000	$ 200,402,000
Number of properties acquired | property										12
Aggregate purchase price for facilities acquired										$ 113,334,000
Initial annual cash rents expected to be generated from acquisition										9,955,000
Mortgage loan						$ 2,600,000				2,600,000
Principal outstanding						495,000,000				495,000,000	565,000,000
Line of credit facility, outstanding borrowings						$ 95,000,000				$ 95,000,000	165,000,000
At-The-Market Offering
Subsequent Event [Line Items]
Issuance of common stock, net (shares) | shares						2,504	4,772	2,989	0	10,265
Average sales price per share (usd per share) | $ / shares						$ 19.98	$ 17.62	$ 16.13	$ 0.00	$ 17.76
Proceeds from the issuance of common stock, net						$ 50,046,000	$ 84,077,000	$ 48,198,000	$ 0	$ 182,321,000
Remaining offering amount available						53,700,000				$ 53,700,000
Multi-service campus
Subsequent Event [Line Items]
Number of properties acquired | property										2
Aggregate purchase price for facilities acquired										$ 27,520,000
Initial annual cash rents expected to be generated from acquisition										2,240,000
Mortgage Loan Receivable
Subsequent Event [Line Items]
Mortgage loan						12,300,000				12,300,000
Unsecured Debt
Subsequent Event [Line Items]
Debt instrument, face amount						$ 300,000,000				$ 300,000,000	$ 300,000,000
Subsequent Event
Subsequent Event [Line Items]
Membership Interest Purchase Agreement, membership interest acquired (percent)													100.00%
Membership Interest Purchase Agreement, special-purpose LLC companies acquired | company													12
Membership Interest Purchase Agreement, contract purchase price													$ 211,000,000
Membership Interest Purchase Agreement, anticipated initial lease yield (percent)													8.90%
Aggregate purchase price for facilities acquired					$ 52,900,000
Initial annual cash rents expected to be generated from acquisition					$ 4,900,000
Number of facilities used to secure mortgage loan | facility					5
Subsequent Event | At-The-Market Offering
Subsequent Event [Line Items]
Issuance of common stock, net (shares) | shares				2,500
Average sales price per share (usd per share) | $ / shares				$ 19.48
Proceeds from the issuance of common stock, net				$ 47,900,000
Remaining offering amount available					$ 5,800,000
Subsequent Event | Skilled nursing facility
Subsequent Event [Line Items]
Membership Interest Purchase Agreement, special-purpose LLC companies acquired | facility													10
Number of properties acquired | facility					4
Subsequent Event | Skilled nursing / senior housing campuses
Subsequent Event [Line Items]
Membership Interest Purchase Agreement, special-purpose LLC companies acquired | campus													2
Subsequent Event | Multi-service campus
Subsequent Event [Line Items]
Number of properties acquired | campus					1
Subsequent Event | Mortgage Loan Receivable
Subsequent Event [Line Items]
Mortgage loan					$ 11,400,000
Mortgage loan receivable interest rate (percent)					9.00%
Loan agreement, number of extension options | extension_option					2
Loan agreement, extension option term					6 months
Subsequent Event | Letter of Credit
Subsequent Event [Line Items]
Subfacility capacity as percentage of available revolving commitments (percent)	10.00%
Subsequent Event | Swingline Loan
Subsequent Event [Line Items]
Subfacility capacity as percentage of available revolving commitments (percent)	10.00%
Subsequent Event | New Revolving Facility | Revolving Credit Facility
Subsequent Event [Line Items]
Line of credit facility, borrowing capacity	$ 600,000,000.0
Maximum Adjusted Consolidated Debt to Consolidated Total Asst Value ratio per covenant	60.00%
Line of credit facility, outstanding borrowings					$ 0
Number of extension options	2
Extension option term	6 months
Subsequent Event | New Term Loan Feb 2019 | Unsecured Debt
Subsequent Event [Line Items]
Debt instrument, face amount	$ 200,000,000
Principal outstanding					$ 200,000,000
Minimum | Subsequent Event | New Revolving Facility | Revolving Credit Facility
Subsequent Event [Line Items]
Facility fee on revolving commitments (percent)	0.15%
Facility fee on revolving commitments based on investment grade ratings (percent)	0.125%
Minimum | Base Rate | Subsequent Event | New Revolving Facility | Revolving Credit Facility
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	0.10%
Minimum | Base Rate | Subsequent Event | New Term Loan Feb 2019 | Unsecured Debt
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	0.50%
Minimum | LIBOR | Subsequent Event | New Revolving Facility | Revolving Credit Facility
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	1.10%
Minimum | LIBOR | Subsequent Event | New Term Loan Feb 2019 | Unsecured Debt
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	1.50%
Maximum | Subsequent Event | New Revolving Facility | Revolving Credit Facility
Subsequent Event [Line Items]
Facility fee on revolving commitments (percent)	0.35%
Facility fee on revolving commitments based on investment grade ratings (percent)	0.30%
Maximum | Base Rate | Subsequent Event | New Revolving Facility | Revolving Credit Facility
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	0.55%
Maximum | Base Rate | Subsequent Event | New Term Loan Feb 2019 | Unsecured Debt
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	1.20%
Maximum | LIBOR | Subsequent Event | New Revolving Facility | Revolving Credit Facility
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	1.55%
Maximum | LIBOR | Subsequent Event | New Term Loan Feb 2019 | Unsecured Debt
Subsequent Event [Line Items]
Basis spread on variable rate (percent)	2.20%