Debt and Financial Instruments - Additional Information (Detail)								1 Months Ended		3 Months Ended				12 Months Ended
		Dec. 01, 2017 USD ($)	Oct. 02, 2017 USD ($)	Jul. 03, 2017 USD ($)	Jun. 01, 2017 USD ($)	Apr. 03, 2017 USD ($)	May 24, 2016 USD ($) Option	Apr. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2016 USD ($) Derivative	Jun. 30, 2016 USD ($) Derivative	Mar. 31, 2014 USD ($) Derivative	Sep. 30, 2013 USD ($) Derivative	Dec. 31, 2017 USD ($) MortgageLoan	Dec. 31, 2016 USD ($) MortgageLoan	Dec. 31, 2015 USD ($)	Mar. 27, 2015 USD ($)
Debt Instrument [Line Items]
Proceeds from Lines of Credit															$ 59,350,000	$ 52,400,000
Outstanding borrowings under revolving credit agreement														$ 181,050,000	201,500,000
Outstanding borrowings under letter of credit														1,500,000
Available borrowing capacity														67,400,000
Average amounts outstanding under our revolving credit agreement														$ 182,400,000	$ 164,200,000	$ 114,300,000
Effective interest rate														2.80%	2.30%	2.10%
Line of credit, fair value of borrowings outstanding														$ 181,100,000
Number of non-recourse mortgages | MortgageLoan														11
Repayments of mortgage loan														$ 61,021,000	$ 3,230,000	$ 17,826,000
Balance of Non Recourse Mortgages	[1]													75,742,000
Mortgage and other notes payable, non-recourse to us, debt premium	[1]													297,000
Financing fees net	[1]													680,000
Interest Rate Cap
Debt Instrument [Line Items]
Number of interest rate cap agreements | Derivative										1	1	2	1
Notional amount										$ 30,000,000	$ 30,000,000	$ 20,000,000	$ 10,000,000
Premium paid										$ 55,000	$ 115,000	$ 134,500	$ 136,000
Expiration date of interest rate cap										Mar. 31, 2019	Mar. 31, 2019	Jan. 31, 2017	Jan. 31, 2017
Level 2
Debt Instrument [Line Items]
Number of non-recourse mortgages | MortgageLoan															15
Mortgage loan fair value														$ 76,300,000	$ 115,700,000
Balance of Non Recourse Mortgages															114,200,000
Mortgage and other notes payable, non-recourse to us, debt premium															436,000
Financing fees net															$ 381,000
Phoenix Children's East Valley Care Center Fixed Rate Mortgage Loan
Debt Instrument [Line Items]
Repayments of mortgage loan		$ 6,100,000
Refinanced the property with fixed rate mortgage loan		$ 9,400,000
Maturity Date		2030-01												2030-01
Balance of Non Recourse Mortgages	[1]													$ 9,400,000
Summerlin Hospital Medical Office Building II fixed rate mortgage loan
Debt Instrument [Line Items]
Repayments of mortgage loan			$ 10,800,000
Auburn Medical II floating rate mortgage loan
Debt Instrument [Line Items]
Repayments of mortgage loan				$ 6,600,000
Medical Center of Western Connecticut fixed rate mortgage loan
Debt Instrument [Line Items]
Repayments of mortgage loan					$ 4,500,000
Peace Health Medical Clinic fixed rate mortgage loan
Debt Instrument [Line Items]
Repayments of mortgage loan						$ 20,200,000
Summerlin Hospital Medical Office Building III floating rate mortgage loan
Debt Instrument [Line Items]
Repayments of mortgage loan									$ 10,300,000
Summerlin Hospital Medical Office Building III fixed rate mortgage loan
Debt Instrument [Line Items]
Refinanced the property with fixed rate mortgage loan								$ 13,200,000
Maturity Date														2024-04
Balance of Non Recourse Mortgages	[1]													$ 13,199,000
LIBOR | Interest Rate Cap
Debt Instrument [Line Items]
Derivative instruments, LIBOR rate										1.50%	1.50%	1.50%	1.50%
Credit Agreement
Debt Instrument [Line Items]
Outstanding borrowing														$ 250,000,000
Credit Agreement
Debt Instrument [Line Items]
Outstanding borrowing							$ 250,000,000										$ 185,000,000
Unsecured revolving amended credit agreement terminated date							2019-03
Number of additional one year extension options | Option							1
Proceeds from Lines of Credit							$ 50,000,000
Credit facility, Interest Rate Terms														one, two, three, or six month LIBOR plus an applicable margin ranging from 1.50% to 2.00% or at the Base Rate plus an applicable margin ranging from 0.50% to 1.00%.
Base rate description														the greatest of: (a) the administrative agent’s prime rate; (b) the federal funds effective rate plus 1/2 of 1%, and; (c) one month LIBOR plus 1%.
Fee payable on unused portion of commitment														0.25%
Credit Agreement | LIBOR
Debt Instrument [Line Items]
Margin points added to the reference rate														1.625%
Credit Agreement | Base Rate
Debt Instrument [Line Items]
Margin points added to the reference rate														0.625%
Credit Agreement | Swingline/Short-Term Loans
Debt Instrument [Line Items]
Outstanding borrowing							20,000,000
Credit Agreement | Letters of Credit
Debt Instrument [Line Items]
Outstanding borrowing							$ 40,000,000
Credit Agreement | Minimum
Debt Instrument [Line Items]
Fee payable on unused portion of commitment							0.20%
Credit Agreement | Minimum | LIBOR
Debt Instrument [Line Items]
Margin points added to the reference rate							1.50%
Margin points added to the base rate							1.00%
Credit Agreement | Minimum | Base Rate
Debt Instrument [Line Items]
Margin points added to the reference rate							0.50%
Credit Agreement | Minimum | Federal Funds Effective Rate
Debt Instrument [Line Items]
Margin points added to the base rate							0.50%
Credit Agreement | Maximum
Debt Instrument [Line Items]
Fee payable on unused portion of commitment							0.40%
Credit Agreement | Maximum | LIBOR
Debt Instrument [Line Items]
Margin points added to the reference rate							2.00%
Credit Agreement | Maximum | Base Rate
Debt Instrument [Line Items]
Margin points added to the reference rate							1.00%

[1] All mortgage loans require monthly principal payments through maturity and either fully amortize or include a balloon principal payment upon maturity.