Real Estate and Lending Activities - Concentrations of Credit Risk - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Significant Acquisitions and Disposals [Line Items]
Revenues	$ 95,961	$ 73,089
European [Member]
Significant Acquisitions and Disposals [Line Items]
Revenues	$ 16,300	$ 5,500
Customer Concentration Risk [Member] | Prime Health Care Services [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of total assets leased	15.20%		12.60%
Percentage of total assets loaned	8.30%		7.40%
Customer Concentration Risk [Member] | Ernest Health, Inc [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of total assets leased	7.90%		7.70%
Percentage of total assets loaned	5.30%		5.30%
Assets, Total [Member]
Significant Acquisitions and Disposals [Line Items]
Number of investment in property	0
Maximum percentage of entity's total assets invested on single property	4.00%
Assets, Total [Member] | Customer Concentration Risk [Member] | MEDIAN Transaction [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of entity revenue from affiliates	11.60%		11.30%
Assets, Total [Member] | Geographic Concentration Risk [Member] | California [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of entity revenue from affiliates	14.30%		14.60%
Assets, Total [Member] | Geographic Concentration Risk [Member] | Texas [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of entity revenue from affiliates	20.50%		20.20%
Assets, Total [Member] | Geographic Concentration Risk [Member] | United States
Significant Acquisitions and Disposals [Line Items]
Percentage of entity revenue from affiliates	80.00%
Assets, Total [Member] | Geographic Concentration Risk [Member] | European [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of entity revenue from affiliates	80.00%		20.00%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Prime Health Care Services [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of entity revenue from affiliates	25.00%	29.10%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | MEDIAN Transaction [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of entity revenue from affiliates	9.50%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Ernest Health, Inc [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of entity revenue from affiliates	15.30%	19.60%