Condensed Combined Statement of Income for Limited Liabilities Accounted for under Equity Method (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity Method Investments And Joint Ventures [Abstract]
Revenues		$ 2,343	$ 2,426	$ 7,256	$ 8,419
Operating expenses		938	933	2,873	3,122
Depreciation and amortization		436	483	1,331	1,547
Interest, net		329	342	985	1,241
Net income		640	668	2,067	2,509
Our share of net income	[1]	$ 351	$ 384	$ 1,205	$ 1,959

[1] Our share of net income for the nine months ended September 30, 2017 includes approximately $284,000 of interest income earned by us on an advance made to Arlington Medical Properties, LLC. This advance was repaid to us effective with the previously mentioned Arlington Medical Properties, LLC transaction during March, 2017, therefore there was no interest income earned by us on this advance subsequent to March, 2017.