Aggregate Principal Amounts Due on Mortgage Notes Payable by Unconsolidated LLCs, Accounted Under Equity Method (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Schedule Of Equity Method Investments [Line Items]
2018		$ 23,347
2019		185,035
2020	[1]	1,688
2021		1,846
2022		11,950
2023 and thereafter		32,926
Total		256,792
Mortgage Loan Balance		27,839	$ 28,367
Equity Method Investments
Schedule Of Equity Method Investments [Line Items]
2018		594
2019		621
2020		5,415
2021		13,549
2022		216
2023 and thereafter		7,444
Total		27,839
Mortgage Loan Balance	[2]	27,839	28,367
Equity Method Investments | FTX MOB Phase II
Schedule Of Equity Method Investments [Line Items]
Mortgage Loan Balance	[2]	$ 5,202	5,301
Maturity Date	[3]	2020-10
Equity Method Investments | Grayson Properties
Schedule Of Equity Method Investments [Line Items]
Mortgage Loan Balance	[2]	$ 14,191	14,438
Maturity Date		2021-09
Equity Method Investments | Brunswick Associates
Schedule Of Equity Method Investments [Line Items]
Mortgage Loan Balance	[2]	$ 8,446	$ 8,628
Maturity Date		2024-12

[1] Includes repayment of $181.1 million of outstanding borrowings under the terms of our $250 million revolving credit agreement.

[2] All mortgage loans require monthly principal payments through maturity and include a balloon principal payment upon maturity.

[3] This loan originally matured on October 1, 2017, and was renewed and extended at a fixed interest rate of 5% with a revised maturity date of October 1, 2020.