Real Estate and Lending Activities - Adeptus Health - Additional Information (Detail) $ in Thousands			1 Months Ended		3 Months Ended	9 Months Ended
	Oct. 01, 2018 Property	Oct. 02, 2017 Facility	Oct. 31, 2018 Facility	Aug. 31, 2018 Facility	Sep. 30, 2018 USD ($) Facility	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Business Acquisition [Line Items]
Real estate impairment charge | $						$ 17,615	$ 1,117
Adeptus Health [Member]
Business Acquisition [Line Items]
Amortization of straight line rent receivables | $						$ 4,000
Number of facilities transitioned		16
Number of properties re-leased				3
Number of transitioned facilities not re-leased					8
Percentage of investment in remaining transition facilities on total assets					1.00%
Real estate impairment charge | $					$ 18,000
Adeptus Health [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Number of properties closed | Property	15
Number of properties re-leased			5